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. |
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. |
unicode | Package unicode provides data and functions to test some properties of Unicode code points. |
unicode/utf8 | Package utf8 implements functions and constants to support text encoded in UTF-8. |