| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| github.com/gorilla/securecookie | Package securecookie encodes and decodes authenticated and optionally encrypted cookie values. |
| io | Package io provides basic interfaces to I/O primitives. |
| 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. |
| os | Package os provides a platform-independent interface to operating system functionality. |
| reflect | Package reflect implements run-time reflection, allowing a program to manipulate objects with arbitrary types. |
| testing/quick | Package quick implements utility functions to help with black box testing. |