| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| github.com/opencontainers/go-digest | Package digest provides a generalized type to opaquely represent message digests and their operations within the registry. |
| io/ioutil | Package ioutil implements some I/O utility functions. |
| net/http | Package http provides HTTP client and server implementations. |
| net/http/httptest | Package httptest provides utilities for HTTP testing. |
| 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. |
| regexp | Package regexp implements regular expression search. |
| strings | Package strings implements simple functions to manipulate UTF-8 encoded strings. |
| sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |