| encoding/gob | Package gob manages streams of gobs - binary values exchanged between an Encoder (transmitter) and a Decoder (receiver). |
| errors | Package errors implements functions to manipulate errors. |
| io | Package io provides basic interfaces to I/O primitives. |
| 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. |
| sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |
| time | Package time provides functionality for measuring and displaying time. |