| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| github.com/stretchr/testify/assert | Package assert provides a set of comprehensive testing tools for use with the normal Go testing system. |
| github.com/stretchr/testify/require | Package require implements the same assertions as the `assert` package but stops test execution when a test fails. |
| github.com/uber/tchannel-go/relay | Package relay contains relaying interfaces for external use. |
| sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |
| testing | Package testing provides support for automated testing of Go packages. |