| cmd/go/internal/base | Package base defines shared basic pieces of the go command, in particular logging and the Command structure. |
| cmd/go/internal/cfg | Package cfg holds configuration shared by multiple parts of the go command. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| os | Package os provides a platform-independent interface to operating system functionality. |
| os/exec | Package exec runs external commands. |
| sort | Package sort provides primitives for sorting slices and user-defined collections. |
| strings | Package strings implements simple functions to manipulate UTF-8 encoded strings. |