| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| maps | Package maps defines various functions useful with maps of any type. |
| net/http | Package http provides HTTP client and server implementations. |
| runtime | Package runtime contains operations that interact with Go's runtime system, such as functions to control goroutines. |
| runtime/debug | Package debug contains facilities for programs to debug themselves while they are running. |
| strings | Package strings implements simple functions to manipulate UTF-8 encoded strings. |
| sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |