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callcount

sync.Once.Do

standard library

The 210th most-called standard-library method by production calls. Called 10,465 times across 697 modules; 4,963 of those run outside tests and generated code.

1% in production calls vs 2026-W39 (4,932 → 4,963)

All of sync → Docs on pkg.go.dev ↗

prod calls
4,963
non-test, non-generated
all calls
10,465
total callsites
modules
697
distinct callers
in loop
3%
of prod calls
in tests
13%
1,405 calls
resolved
100%
to a known target

resolution mix

How each call resolves

How each call was attributed. Only resolved kinds, where the target function is known, count toward the ranking. Interface dispatch and unresolved receivers are reported separately and never guessed. Read the taxonomy →

  • Concrete method99%A method on a value whose type is known exactly.
  • Embedded method<1%Reached through an embedded type.

estimate

Experimental

Estimated relative cost

Roughly 0.00× the estimated relative cost of fmt.Sprintf . Benchmarked at 1.98 ns/op × 4,963 production calls, normalized so fmt.Sprintf = 1.0.

This is not dollars and not a verdict. Per-op time depends heavily on inputs (argument sizes, contention, patterns), the benchmark ran on a single machine (darwin/arm64 (Apple Silicon), go1.26.0), and static call counts are not runtime frequency. How this is estimated →

who calls this

Notable callers

Production calls into Once.Do from notable Go projects. Open one on the map to see what else it hammers.

where it's called

Callsites in the wild

12 representative callsites of 10,465, prioritizing in-loop and non-test usage. We link to source, never display it.

Once.Do · 12 of 10,465 callsites

top callers

The modules that reach for it

The modules that call Once.Do most in this snapshot.

  • github.com/yandex-cloud/go-genproto9639%
  • google.golang.org/genproto6576%
  • github.com/envoyproxy/go-control-plane/envoy6336%
  • github.com/kubernetes/kubernetes2833%
  • github.com/esengine/DeepSeek-Reasonix1922%

siblings

More from sync

The other most-called members in this package. See all →