| bytes | Package bytes implements functions for the manipulation of byte slices. |
| cmd/go/internal/fsys | Package fsys implements a virtual file system that the go command uses to read source file trees. |
| cmd/go/internal/par | |
| context | Package context defines the Context type, which carries deadlines, cancellation signals, and other request-scoped values across API boundaries and between processes. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| go/build | Package build gathers information about Go packages. |
| internal/buildcfg | Package buildcfg provides access to the build configuration described by the current environment. |
| internal/cfg | Package cfg holds configuration shared by the Go command and internal/testenv. |
| io | Package io provides basic interfaces to I/O primitives. |
| os | Package os provides a platform-independent interface to operating system functionality. |
| os/exec | Package exec runs external commands. |
| path/filepath | Package filepath implements utility routines for manipulating filename paths in a way compatible with the target operating system-defined file paths. |
| runtime | Package runtime contains operations that interact with Go's runtime system, such as functions to control goroutines. |
| strings | Package strings implements simple functions to manipulate UTF-8 encoded strings. |
| sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |