| errors | Package errors implements functions to manipulate errors. |
| internal/oserror | Package oserror defines errors values used in the os package. |
| internal/poll | Package poll supports non-blocking I/O on file descriptors with polling. |
| internal/syscall/unix | |
| internal/testlog | Package testlog provides a back-channel communication path between tests and package os, so that cmd/go can see which environment variables and files a test consults. |
| 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. |
| sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |
| sync/atomic | Package atomic provides low-level atomic memory primitives useful for implementing synchronization algorithms. |
| syscall | Package syscall contains an interface to the low-level operating system primitives. |
| time | Package time provides functionality for measuring and displaying time. |