The main package is Go’s special executable package. When a directory contains package main, the compiler searches its files for a main function and produces one independently runnable executable. section 2.4.5
Other packages can be named for their purpose and imported as libraries. The main package identifies where an application starts, while package boundaries organize concerns and control visibility. section 2.4.5 section 11.1.1
Use main package deliberately when structuring executable projects:
- Keep each executable’s main package and main function in its own subdirectory, commonly under cmd, such as cmd/myapp/main.go. section 11.1.1
- Share reusable logic through purpose-specific packages rather than placing every concern in main; Go rejects circular package dependencies. section 11.1.1
- Use internal for implementation code that external applications must not import; the compiler enforces its directory-tree visibility boundary. section 11.1.1
Minimal executable declaration
A file beginning with package main declares participation in an executable package. Add a main function to provide the program’s starting point; the compiler then emits a single runnable executable. section 2.4.5
Listing 2.8 Declaring package main
package main
View the minimal package declaration that marks a Go file as belonging to the executable package. section 2.4.5
