| bytes | Package bytes implements functions for the manipulation of byte slices. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| io | Package io provides basic interfaces to I/O primitives. |
| runtime | Package runtime contains operations that interact with Go's runtime system, such as functions to control goroutines. |
| strconv | Package strconv implements conversions to and from string representations of basic data types. |
| sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |
| unicode/utf8 | Package utf8 implements functions and constants to support text encoded in UTF-8. |