The Go Programming Language

2.6 Packages and Files

Packages in Go serve the same purposes as libraries or modules in other languages, supporting modularity, encapsulation, separate compilation, and reuse. The source code for a package resides in one or more .go files, usually in a directory whose name ends with the import path; for instance, the files of the gopl.io/ch1/helloworld package are stored in directory $GOPATH/src/gopl.io/ch1/helloworld.

Each package serves as a separate name space for its declarations. Within the image package, for example, the identifier Decode refers to a different function than does the same identifier in the unicode/utf16 package. To refer to a function from outside its package, we must qualify the identifier to make explicit whether ...