github.com/googleapis/gax-go/v2 v2.19.0: Invoke

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify Invoke in pkg:golang/github.com/googleapis/gax-go/v2@v2.19.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/googleapis/gax-go/v2@v2.19.0
Demonstrate these symbols/APIs:
  - Invoke

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:d5bebc3a3ad66ed85537671db2327b64c7f0f86b989dfaa810aabfdcb5674738","contract":["gax.Invoke executes an APICall once and returns nil when it succeeds on the first attempt","gax.Invoke with gax.WithRetry and gax.OnErrorFunc retries transient errors until the APICall returns nil","gax.Invoke immediately returns non-retryable errors without additional retry attempts","gax.Invoke with gax.WithTimeout applies a deadline to the context passed to the APICall"],"goal":"verify Invoke in pkg:golang/github.com/googleapis/gax-go/v2@v2.19.0","kind":"HOW","packages":["pkg:golang/github.com/googleapis/gax-go/v2@v2.19.0"],"schemaVersion":1,"symbols":["Invoke"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/googleapis/gax-go/v2@v2.19.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/googleapis/gax-go/v2@v2.19.0","symbols":["Invoke"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/googleapis/gax-go/v2 v2.19.0

require (
	github.com/cespare/xxhash/v2 v2.3.0 // indirect
	github.com/go-logr/logr v1.4.3 // indirect
	github.com/go-logr/stdr v1.2.2 // indirect
	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
	go.opentelemetry.io/otel v1.42.0 // indirect
	go.opentelemetry.io/otel/metric v1.42.0 // indirect
	go.opentelemetry.io/otel/trace v1.42.0 // indirect
	golang.org/x/net v0.52.0 // indirect
	golang.org/x/sys v0.42.0 // indirect
	golang.org/x/text v0.35.0 // indirect
	google.golang.org/api v0.272.0 // indirect
	google.golang.org/genproto/googleapis/rpc v0.0.0-20260316180232-0b37fe3546d5 // indirect
	google.golang.org/grpc v1.79.2 // indirect
	google.golang.org/protobuf v1.36.11 // indirect
)

github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
github.com/go-logr/logr v1.4.3 h1:CjnDlHq8ikf6E492q6eKboGOC0T8CDaOvkHCIg8idEI=
github.com/go-logr/logr v1.4.3/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
github.com/golang/protobuf v1.5.4 h1:i7eJL8qZTpSEXOPTxNKhASYpMn+8e5Q6AdndVa1dWek=
github.com/golang/protobuf v1.5.4/go.mod h1:lnTiLA8Wa4RWRcIUkrtSVa5nRhsEGBg48fD6rSs7xps=
github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
github.com/googleapis/gax-go/v2 v2.19.0 h1:fYQaUOiGwll0cGj7jmHT/0nPlcrZDFPrZRhTsoCr8hE=
github.com/googleapis/gax-go/v2 v2.19.0/go.mod h1:w2ROXVdfGEVFXzmlciUU4EdjHgWvB5h2n6x/8XSTTJA=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
go.opentelemetry.io/otel v1.42.0 h1:lSQGzTgVR3+sgJDAU/7/ZMjN9Z+vUip7leaqBKy4sho=
go.opentelemetry.io/otel v1.42.0/go.mod h1:lJNsdRMxCUIWuMlVJWzecSMuNjE7dOYyWlqOXWkdqCc=
go.opentelemetry.io/otel/metric v1.42.0 h1:2jXG+3oZLNXEPfNmnpxKDeZsFI5o4J+nz6xUlaFdF/4=
go.opentelemetry.io/otel/metric v1.42.0/go.mod h1:RlUN/7vTU7Ao/diDkEpQpnz3/92J9ko05BIwxYa2SSI=
go.opentelemetry.io/otel/sdk v1.42.0 h1:LyC8+jqk6UJwdrI/8VydAq/hvkFKNHZVIWuslJXYsDo=
go.opentelemetry.io/otel/sdk v1.42.0/go.mod h1:rGHCAxd9DAph0joO4W6OPwxjNTYWghRWmkHuGbayMts=
go.opentelemetry.io/otel/sdk/metric v1.42.0 h1:D/1QR46Clz6ajyZ3G8SgNlTJKBdGp84q9RKCAZ3YGuA=
go.opentelemetry.io/otel/sdk/metric v1.42.0/go.mod h1:Ua6AAlDKdZ7tdvaQKfSmnFTdHx37+J4ba8MwVCYM5hc=
go.opentelemetry.io/otel/trace v1.42.0 h1:OUCgIPt+mzOnaUTpOQcBiM/PLQ/Op7oq6g4LenLmOYY=
go.opentelemetry.io/otel/trace v1.42.0/go.mod h1:f3K9S+IFqnumBkKhRJMeaZeNk9epyhnCmQh/EysQCdc=
golang.org/x/net v0.52.0 h1:He/TN1l0e4mmR3QqHMT2Xab3Aj3L9qjbhRm78/6jrW0=
golang.org/x/net v0.52.0/go.mod h1:R1MAz7uMZxVMualyPXb+VaqGSa3LIaUqk0eEt3w36Sw=
golang.org/x/sys v0.42.0 h1:omrd2nAlyT5ESRdCLYdm3+fMfNFE/+Rf4bDIQImRJeo=
golang.org/x/sys v0.42.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
golang.org/x/text v0.35.0 h1:JOVx6vVDFokkpaq1AEptVzLTpDe9KGpj5tR4/X+ybL8=
golang.org/x/text v0.35.0/go.mod h1:khi/HExzZJ2pGnjenulevKNX1W67CUy0AsXcNubPGCA=
gonum.org/v1/gonum v0.16.0 h1:5+ul4Swaf3ESvrOnidPp4GZbzf0mxVQpDCYUQE7OJfk=
gonum.org/v1/gonum v0.16.0/go.mod h1:fef3am4MQ93R2HHpKnLk4/Tbh/s0+wqD5nfa6Pnwy4E=
google.golang.org/api v0.272.0 h1:eLUQZGnAS3OHn31URRf9sAmRk3w2JjMx37d2k8AjJmA=
google.golang.org/api v0.272.0/go.mod h1:wKjowi5LNJc5qarNvDCvNQBn3rVK8nSy6jg2SwRwzIA=
google.golang.org/genproto v0.0.0-20260316180232-0b37fe3546d5 h1:JNfk58HZ8lfmXbYK2vx/UvsqIL59TzByCxPIX4TDmsE=
google.golang.org/genproto v0.0.0-20260316180232-0b37fe3546d5/go.mod h1:x5julN69+ED4PcFk/XWayw35O0lf/nGa4aNgODCmNmw=
google.golang.org/genproto/googleapis/api v0.0.0-20260316180232-0b37fe3546d5 h1:CogIeEXn4qWYzzQU0QqvYBM8yDF9cFYzDq9ojSpv0Js=
google.golang.org/genproto/googleapis/api v0.0.0-20260316180232-0b37fe3546d5/go.mod h1:EIQZ5bFCfRQDV4MhRle7+OgjNtZ6P1PiZBgAKuxXu/Y=
google.golang.org/genproto/googleapis/rpc v0.0.0-20260316180232-0b37fe3546d5 h1:aJmi6DVGGIStN9Mobk/tZOOQUBbj0BPjZjjnOdoZKts=
google.golang.org/genproto/googleapis/rpc v0.0.0-20260316180232-0b37fe3546d5/go.mod h1:4Hqkh8ycfw05ld/3BWL7rJOSfebL2Q+DVDeRgYgxUU8=
google.golang.org/grpc v1.79.2 h1:fRMD94s2tITpyJGtBBn7MkMseNpOZU8ZxgC3MMBaXRU=
google.golang.org/grpc v1.79.2/go.mod h1:KmT0Kjez+0dde/v2j9vzwoAScgEPx/Bw1CYChhHLrHQ=
google.golang.org/protobuf v1.36.11 h1:fV6ZwhNocDyBLK0dj+fg8ektcVegBBuEolpbTQyBNVE=
google.golang.org/protobuf v1.36.11/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

{
  "schemaVersion": 1,
  "goal": "verify Invoke in pkg:golang/github.com/googleapis/gax-go/v2@v2.19.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/googleapis/gax-go/v2@v2.19.0"
  ],
  "symbols": [
    "Invoke"
  ]
}

package main

import (
	"context"
	"errors"
	"fmt"
	"os"
	"time"

	gax "github.com/googleapis/gax-go/v2"
)

func main() {
	ctx := context.Background()

	// 1. Single call without retry options succeeds on first attempt
	attempts := 0
	err := gax.Invoke(ctx, func(c context.Context, settings gax.CallSettings) error {
		attempts++
		return nil
	})
	if err != nil || attempts != 1 {
		fmt.Fprintf(os.Stderr, "expected 1 attempt and nil error, got %d and %v\n", attempts, err)
		os.Exit(1)
	}

	// 2. Call with WithRetry and OnErrorFunc retries transient error until nil
	errTransient := errors.New("transient error")
	errPermanent := errors.New("permanent error")

	attempts = 0
	retryOpt := gax.WithRetry(func() gax.Retryer {
		return gax.OnErrorFunc(gax.Backoff{
			Initial:    time.Millisecond,
			Max:        5 * time.Millisecond,
			Multiplier: 2,
		}, func(e error) bool {
			return errors.Is(e, errTransient)
		})
	})

	err = gax.Invoke(ctx, func(c context.Context, settings gax.CallSettings) error {
		attempts++
		if attempts < 3 {
			return errTransient
		}
		return nil
	}, retryOpt)
	if err != nil || attempts != 3 {
		fmt.Fprintf(os.Stderr, "expected 3 attempts and nil error, got %d and %v\n", attempts, err)
		os.Exit(1)
	}

	// 3. Non-retryable error stops immediately without further retries
	attempts = 0
	err = gax.Invoke(ctx, func(c context.Context, settings gax.CallSettings) error {
		attempts++
		return errPermanent
	}, retryOpt)
	if !errors.Is(err, errPermanent) || attempts != 1 {
		fmt.Fprintf(os.Stderr, "expected 1 attempt and permanent error, got %d and %v\n", attempts, err)
		os.Exit(1)
	}

	// 4. WithTimeout sets a deadline on the context passed to APICall
	var hadDeadline bool
	err = gax.Invoke(ctx, func(c context.Context, settings gax.CallSettings) error {
		_, hadDeadline = c.Deadline()
		return nil
	}, gax.WithTimeout(50*time.Millisecond))
	if err != nil || !hadDeadline {
		fmt.Fprintf(os.Stderr, "expected deadline set by WithTimeout, got hadDeadline=%v err=%v\n", hadDeadline, err)
		os.Exit(1)
	}
}