| context | Package context defines the Context type, which carries deadlines, cancellation signals, and other request-scoped values across API boundaries and between processes. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| go.opencensus.io/metric/metricdata | Package metricdata contains the metrics data model. |
| go.opencensus.io/metric/metricproducer | |
| go.opencensus.io/trace | Package trace contains support for OpenCensus distributed tracing. |
| sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |
| time | Package time provides functionality for measuring and displaying time. |