| image | Package image implements a basic 2-D image library. |
| image/color | Package color implements a basic color library. |
| image/draw | Package draw provides image composition functions. |
| math | Package math provides basic constants and mathematical functions. |
| math/rand | Package rand implements pseudo-random number generators suitable for tasks such as simulation, but it should not be used for security-sensitive work. |
| 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. |