What the call data turns up

The function Go runs most inside loops

encoding/json.Unmarshal sits inside a loop at 51% of its 172,212 production calls.

encoding/json.Unmarshal

Half of all in-loop work comes from a handful of functions

Half of every production call that runs inside a loop traces back to just 65 of the 9,220 ranked functions.

The busy function that almost never leaves a loop

Among functions with real volume, time.Sleep runs inside a loop more than any other, 62% of its 7,421 production calls.

time.Sleep

The function with the widest reach across the ecosystem

fmt.Sprintf is called from 1,690 of the 2,029 modules in the corpus, roughly 1 in every 1.2.

fmt.Sprintf

The function one codebase hammers harder than anyone

github.com/Azure/go-autorest/autorest.NewErrorWithError makes 215,125 production calls from just 2 modules, about 107,563 calls per module. High volume, almost no breadth.

github.com/Azure/go-autorest/autorest.NewErrorWithError

True ubiquity is rare

Only 20 functions are called in at least half of the 2,029 modules in the corpus. Almost everything else is niche.

The function nearly every project reaches for first

fmt.Errorf is the single most-called function in 33 of the 47 projects mapped, the common denominator of Go.

fmt.Errorf

The heaviest caller of them all

Kubernetes makes 515,398 production calls across 39 modules, more than any other project we mapped.

Kubernetes

Kubernetes' signature call

Kubernetes leans on k8s.io/kubernetes/test/e2e/framework.ExpectNoError harder than the field does. That is 10,641 production calls from its own modules.

k8s.io/kubernetes/test/e2e/framework.ExpectNoError

Terraform's signature call

Terraform leans on github.com/aws/aws-sdk-go/aws.String harder than the field does. That is 6,492 production calls from its own modules.

github.com/aws/aws-sdk-go/aws.String

TiDB's signature call

TiDB leans on github.com/juju/errors.Trace harder than the field does. That is 3,722 production calls from its own modules.

github.com/juju/errors.Trace

HashiCorp's signature call

HashiCorp leans on github.com/hashicorp/boundary/internal/errors.New harder than the field does. That is 3,611 production calls from its own modules.

github.com/hashicorp/boundary/internal/errors.New

Go's busiest interface method

io.Closer.Close is dispatched more than any other interface method, 58,482 calls that could land on any implementation.

io.Closer.Close

Interfaces are everywhere, but they carry little traffic

Just 4% of the 13,841,342 calls in the corpus go through an interface. Most Go is concrete.

Everyone writes through the same shape

979 modules call io.Writer.Write, and 99% of those calls are dispatched. The target is a file, a buffer, or a socket, decided at runtime.

io.Writer.Write

The priciest hot path in the corpus

Weighted by how often it runs, encoding/json.Unmarshal is the corpus's most expensive hot path, about 36x the per-call cost of fmt.Sprintf, and 51% of its calls run inside a loop.

encoding/json.Unmarshal

The cheapest call we benchmarked

Of the hot-path functions we benchmarked on darwin/arm64 (Apple Silicon), strconv.FormatBool is the cheapest, about 1.9 nanoseconds per call.

strconv.FormatBool

Go programs compile their patterns once, not in the loop

regexp.MustCompile costs about 31x a fmt.Sprintf per call, but only 3% of its calls sit inside a loop. The expensive part stays out of the hot path.

regexp.MustCompile

The most test-bound function in the corpus

testing.common.Fatalf is called 443,834 times from tests, 98% of all its calls.

testing.common.Fatalf

The third-party helper the test suite can't live without

github.com/stretchr/testify/require.NoError is the most-called third-party function in tests, 292,333 calls, 96% of them in test files.

github.com/stretchr/testify/require.NoError

Even a workhorse leans on code generators

27% of fmt.Errorf's 570,823 calls are emitted by code generators. The rest are hand-written.

fmt.Errorf

How much of Go is written by code generators

8% of every call in the corpus lives in generated code, such as protobuf and cloud SDKs.

The median Go function is barely called at all

Half of the 9,220 ranked functions are called 130 times or fewer in production. The famous ones are the exception.

A tiny fraction of functions does most of the work

The busiest 1% of functions, 92 of them, account for 53% of every production call. A textbook power law.

Ten functions carry a fifth of everything

Just ten functions account for 21% of all 7,434,386 production calls in the corpus.

The standard library punches far above its weight

The 1,525 standard-library functions are 17% of the catalog but do 45% of all production work.

Most catalogued functions are barely used

0% of the 9,220 ranked functions are called at most once in production code, catalogued, but rarely reached for.