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What you will learn in Go by Example

Programmer's guide to idiomatic and testable code

by Inanc Gumus

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Chapter by chapter

Concepts explained in this book

• contextcontext.Context is a Go standard-library interface that carries cancellation signals, deadlines, and request-scoped values across call boundaries.
• testA test case is a defined test scenario consisting of inputs, execution conditions, and expected behavior or results.
• pipelineA pipeline is an ordered sequence of connected processing stages in which results from one stage are passed to subsequent stages.
• command-line argumentA command-line argument is a string value supplied to a program by the operating system when the program starts.
• middlewareMiddleware is a software pattern in which a component wraps a handler or processing component to add behavior before, after, or around the wrapped component's execution.
• io.Writerio.Writer is a Go interface whose Write method accepts a byte sequence and returns the number of bytes written and an error.
• iteratorAn iterator is an abstraction that lets a consumer retrieve values from a sequence one at a time through a standardized interface.
• type assertionA runtime type assertion is a Go expression that checks and retrieves the concrete value represented by an interface value at run time.
• closureA closure is a function that retains access to variables in its surrounding lexical scope after the enclosing function returns.
• benchmarkA benchmark is a repeatable performance measurement that runs a piece of code, usually many times, to assess its execution characteristics.
• handlerA handler is a software component that receives an operation or request and produces the corresponding processing result.
• channelA channel is a typed Go communication conduit through which goroutines send and receive values while synchronizing.
• subtestA subtest is an independently named test executed as part of a parent test and reported separately.
• value parserA value parser is a function that converts a string flag value to a specified Go type, assigns the result to a variable, and reports parsing errors.
• goroutineA goroutine is a lightweight Go execution unit that runs a function concurrently with other goroutines.
• GoGo is a statically typed, compiled programming language designed for simplicity, efficient execution, and reliable software development.
• task cancellationA cancellation signal is an indication that an ongoing operation should stop because it is no longer needed or cannot continue.
• testabilityTestability is the degree to which software can be tested effectively and independently.
• implicit interface satisfactionAn implicit interface is a Go interface that a type satisfies automatically by implementing all of the interface's methods without an explicit declaration.
• ShortenerA shortener service is a service that converts URLs into shorter keys and resolves those keys back to URLs.
• zero valueA zero value is the default value assigned to a Go variable when no explicit initializer is provided.
• database/sqldatabase/sql is Go's standard library package that provides a database-independent API for working with SQL databases.
• concurrencyConcurrency is the ability to structure a program so that multiple execution activities can make progress during overlapping periods.
• flag.FlagSetflag.FlagSet is a Go flag package type that defines a set of command-line flags and manages their parsing and usage behavior.
• database driverA database driver is software that implements a database access interface for communicating with a particular database technology.
• http.RoundTripperhttp.RoundTripper is a Go interface whose RoundTrip method executes a single HTTP transaction and returns the response or an error.
• memory allocationA memory allocation is a reservation of heap memory made during program execution, commonly counted per operation in performance measurements.
• table-driven testTable-driven testing is a testing technique that represents multiple test cases as data and executes a common test procedure for each case.
• referenceA pointer is a Go value that contains the memory address of another value and permits indirect access to it.
• strings.Builderstrings.Builder is a Go standard-library type that efficiently accumulates bytes or strings and converts the accumulated data to a string.
• errors.Iserrors.Is is a Go standard-library function that reports whether an error or any error in its wrapping chain matches a target error.
• correlation idA trace ID is an identifier that correlates processing and log records belonging to the same request or distributed operation.
• circular dependencyAn import cycle is a circular dependency among Go packages that prevents the package import graph from being acyclic.
• httptestThe httptest package is Go's standard-library package for testing HTTP clients and servers with utilities such as in-memory test servers, requests, and responses.
• standard libraryA standard library is a collection of reusable modules, types, functions, APIs, and other facilities distributed with a programming language implementation or platform.
• compositionComposition is a design approach that builds larger abstractions by combining smaller components rather than inheriting implementation from a base type.
• race conditionA race condition is a concurrency defect in which program behavior depends on the timing or ordering of operations accessing shared state.
• optional interfaceAn optional interface is an interface whose support a type may provide to expose additional behavior without being required by the base contract.
• flag packageThe flag package is Go's standard package for parsing command-line flags and defining their names, defaults, and value handling.
• polymorphismPolymorphism is the ability to treat instances of different types through a shared type or interface while preserving type-specific behavior.
• dispatcherA dispatcher is a pipeline stage that launches concurrent workers to send requests and collect their results.
• t.Errorftesting.T.Errorf records a formatted test failure while allowing the calling test function to continue.
• concrete typeA concrete type is a non-interface Go type that specifies values with an underlying representation and may have methods.
• parsingParse is a book-specific function that parses a URL into a URL value and reports an error when the URL lacks a scheme.
• errors.Aserrors.As is a Go standard-library function that searches an error chain for a value assignable to a specified error type and stores the result.
• connection poolingA connection pool is a managed collection of reusable network connections maintained to avoid repeatedly establishing new connections.
• lockingLocking is a concurrency-control technique that restricts access to a shared resource or protected operation to prevent conflicting concurrent access.
• aspectInterceptor is a book-specific wrapper type that intercepts response-writing behavior while retaining access to the wrapped response writer.
• http.Serverhttp.Server is Go's HTTP server type that accepts network connections and dispatches requests to a configured handler.
• multi-tier applicationA layered package structure is an organization in which packages depend only on packages in lower layers of the structure.
• idiomatic coding styleA programming idiom is a customary way of expressing a solution or structure in a particular programming language.
• style guideA programming convention is a commonly accepted practice for organizing or expressing code within a language community.
• http.ResponseWriterhttp.ResponseWriter is the Go HTTP interface through which a handler constructs an HTTP response and accesses connection-related response behavior.
• example testAn example test is a Go test function whose output serves both as an executable check and as documentation for an example of using an API.
• go testgo test is the Go command that builds and runs tests for Go packages.
• yield functionA yield function is a consumer-provided callback that receives one iterator value and returns a boolean indicating whether iteration should continue.
• Fatalftesting.T.Fatalf records a formatted test failure and stops execution of the calling test function.
• TextMarshalerTextMarshaler is a Go interface for types that can encode themselves as text.
• flag.Valueflag.Value is a Go interface for parsing a command-line flag string and assigning the resulting value to an associated variable.
• struct embeddingField embedding is the inclusion of an anonymous field in a Go struct so the embedded field and its members can be promoted.
• packageA Go package is a collection of Go source files that provides a namespace and compilation unit.
• command-line toolA command-line tool is a software program operated through textual commands in a shell or terminal.
• testing.B.Looptesting.B.Loop is a Go testing package method that executes benchmark iterations while preventing compiler optimizations from invalidating the measured code.
• dependency injectionDependency injection is a software design technique in which required dependencies are supplied to a component from outside rather than created internally.
• sql.DBsql.DB is the database/sql concrete type that provides database operations while managing a pool of database connections.
• UnwrapUnwrap is a method that exposes the underlying wrapped object or response writer for access to its additional behavior.
• io.Readerio.Reader is a Go interface whose Read method fills a caller-provided byte slice with incoming data and reports the amount read and any error.
• consumer-driven interfaceA consumer-driven interface is an interface declared around the specific operations required by its consuming client rather than around all operations of an implementation.
• stutteringStuttering is repetitive naming in which a package-qualified identifier redundantly repeats information already conveyed by the package name.
• error chainAn error chain is a linked sequence of wrapped Go error values that preserves an underlying cause and added context.
• init functionAn init function is a special Go function that runs automatically during package initialization before program execution begins.
• testing.T.Runtesting.T.Run is a Go testing API method that executes a named subtest and reports its result independently.
• RESTREST is an architectural approach for designing networked resources and interactions through uniform operations, commonly over HTTP.
• interface embeddingInterface embedding is the inclusion of one interface's method set in another interface by naming the embedded interface.
• URLA URL is a structured identifier for locating a resource through a network-access scheme, host, and optional path.
• throttlerA throttler is a concurrency component that spaces messages or operations by delaying their forwarding or execution.
• serverAn HTTP server is software that accepts and processes Hypertext Transfer Protocol requests and returns responses.
• producerA producer is a pipeline stage that creates and delivers messages to a subsequent stage.
• iter.Seqiter.Seq is Go's generic standard-library function type representing a push iterator whose yield callback receives values and returns whether iteration should continue.
• net/http packageThe http package is Go's standard-library package providing HTTP client and server implementations and related types.
• go:embed directiveFile embedding is the Go compiler feature that incorporates external file contents into a program's variables and compiled binary.
• http.HandlerFunchttp.HandlerFunc is a Go function type that adapts a function with an HTTP handler signature to the http.Handler interface.
• push iteratorA push iterator is an iteration abstraction in which a producer invokes a consumer with each successive value rather than having the consumer request values.
• custom flag parserA custom flag parser is program logic that interprets command-line flag names and values and assigns the parsed values to configuration fields.
• SQLiteSQLite is an embedded relational database engine that stores data in a local file or in memory without requiring a separate server process.
• StringA Go string is an immutable sequence of bytes whose contents can be represented without copying when sliced.
• help messageA usage message is command-line help text describing a program's available options, types, defaults, and invocation syntax.
• io.Copyio.Copy is a Go standard-library function that copies bytes from an io.Reader to an io.Writer and returns the number of bytes copied and any error.
• SQLAn SQL query is a statement expressed in SQL that requests or modifies data in a relational database.
• dependencyA software dependency is an external component or runtime resource required by a program to function.
• rwmutexRWMutex is a Go synchronization type that permits concurrent read access while allowing only one writer at a time.
• integration testAn integration test verifies behavior involving interactions between a program and external systems or components.
• variadic argumentsA variadic function is a function that accepts a variable number of arguments through a variadic parameter represented inside the function as a slice.
• http.Transporthttp.Transport is a Go HTTP transport implementation that performs request transmission and maintains a pool of reusable network connections.
• call by valuePass-by-value is a parameter-passing semantics in which a function receives a copy of each argument's value.
• command-line parsingA command-line parser is software that interprets command-line arguments and flags according to a defined syntax.
• http.Responsehttp.Response is the Go standard-library type representing an HTTP response, including its status, headers, and body.
• http.NewRequesthttptest.NewRequest is a Go standard-library function that constructs an HTTP request for use in server tests and panics if its method or target is invalid.
• FlagSet.VarFlagSet.Var is a method that registers a named command-line flag backed by a value implementing the flag.Value interface.
• roundTripperFuncA roundTripperFunc is a function type that adapts a function with a RoundTripper-compatible signature into a RoundTripper implementation.
• backing arrayA backing array is the array that stores the elements referenced by a Go slice.
• driver.Valuerdriver.Valuer is a Go interface implemented by types that convert themselves into values accepted by a database driver.
• error wrappingError wrapping is the practice of adding contextual information to an error while preserving the original error for later inspection.
• range loopA for-range loop is a Go loop construct that iterates over values produced by a rangeable expression, including supported iterator functions.
• %w error verbThe %w error verb is a Go formatting directive that records an operand as the wrapped cause of a returned error.

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