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. |
runtime | Package runtime contains operations that interact with Go's runtime system, such as functions to control goroutines. |
sort | Package sort provides primitives for sorting slices and user-defined collections. |
strconv | Package strconv implements conversions to and from string representations of basic data types. |
strings | Package strings implements simple functions to manipulate UTF-8 encoded strings. |
time | Package time provides functionality for measuring and displaying time. |