Go

Go is a first-class language for CloudMock (CloudMock itself is written in Go). The cloudmock Go SDK provides HTTP interceptor middleware and trace propagation. For AWS-only usage, configure aws-sdk-go-v2 to point at the CloudMock gateway.

cloudmock Go SDK

Install

go get github.com/Viridian-Inc/cloudmock/sdk/go

Initialize

Call cloudmock.Init() early in your application startup. This registers an HTTP transport interceptor that captures outgoing AWS API calls and forwards telemetry to the CloudMock admin API.

package main

import (
    "log"
    cloudmock "github.com/Viridian-Inc/cloudmock/sdk/go"
)

func main() {
    err := cloudmock.Init(cloudmock.Config{
        AdminURL:    "http://localhost:4599",
        ServiceName: "my-api",
    })
    if err != nil {
        log.Fatal(err)
    }
    defer cloudmock.Shutdown()

    // Your application code here
}

HTTP interceptor

The SDK wraps Go’s http.DefaultTransport to intercept outgoing requests to the CloudMock gateway. All AWS SDK calls that use the default HTTP client are automatically captured.

If you use a custom http.Client, wrap its transport:

client := &http.Client{
    Transport: cloudmock.WrapTransport(http.DefaultTransport),
}

net/http middleware

For HTTP servers, the SDK provides middleware that traces inbound requests:

import "github.com/Viridian-Inc/cloudmock/sdk/go"

mux := http.NewServeMux()
mux.HandleFunc("/users", handleUsers)

handler := cloudmock.Middleware(mux)
http.ListenAndServe(":8080", handler)

What gets captured

• Inbound HTTP requests — Method, path, status code, duration.
• Outbound AWS calls — Service, action, latency, status code. Automatically detected from request headers.
• Trace context — A trace ID is propagated from inbound requests to outbound AWS calls.
• Service identity — The ServiceName appears as a node in the Topology view.

aws-sdk-go-v2 endpoint configuration

If you do not need the CloudMock Go SDK (for example, in a CLI tool or Lambda function), configure aws-sdk-go-v2 directly:

Environment variable

export AWS_ENDPOINT_URL=http://localhost:4566
export AWS_ACCESS_KEY_ID=test
export AWS_SECRET_ACCESS_KEY=test
export AWS_DEFAULT_REGION=us-east-1

Programmatic configuration

package main

import (
    "context"
    "fmt"

    "github.com/aws/aws-sdk-go-v2/aws"
    "github.com/aws/aws-sdk-go-v2/config"
    "github.com/aws/aws-sdk-go-v2/credentials"
    "github.com/aws/aws-sdk-go-v2/service/s3"
    "github.com/aws/aws-sdk-go-v2/service/dynamodb"
    "github.com/aws/aws-sdk-go-v2/service/dynamodb/types"
)

func main() {
    cfg, err := config.LoadDefaultConfig(context.TODO(),
        config.WithRegion("us-east-1"),
        config.WithCredentialsProvider(
            credentials.NewStaticCredentialsProvider("test", "test", ""),
        ),
        config.WithBaseEndpoint("http://localhost:4566"),
    )
    if err != nil {
        panic(err)
    }

    // S3 -- must use path style
    s3Client := s3.NewFromConfig(cfg, func(o *s3.Options) {
        o.UsePathStyle = true
    })

    _, err = s3Client.CreateBucket(context.TODO(), &s3.CreateBucketInput{
        Bucket: aws.String("my-bucket"),
    })
    if err != nil {
        panic(err)
    }
    fmt.Println("S3 bucket created")

    // DynamoDB
    ddbClient := dynamodb.NewFromConfig(cfg)
    _, err = ddbClient.CreateTable(context.TODO(), &dynamodb.CreateTableInput{
        TableName: aws.String("Users"),
        KeySchema: []types.KeySchemaElement{
            {AttributeName: aws.String("UserId"), KeyType: types.KeyTypeHash},
        },
        AttributeDefinitions: []types.AttributeDefinition{
            {AttributeName: aws.String("UserId"), AttributeType: types.ScalarAttributeTypeS},
        },
        BillingMode: types.BillingModePayPerRequest,
    })
    if err != nil {
        panic(err)
    }
    fmt.Println("DynamoDB table created")
}

Conditional endpoint

func loadConfig() (aws.Config, error) {
    opts := []func(*config.LoadOptions) error{
        config.WithRegion("us-east-1"),
    }

    if endpoint := os.Getenv("CLOUDMOCK_ENDPOINT"); endpoint != "" {
        opts = append(opts,
            config.WithBaseEndpoint(endpoint),
            config.WithCredentialsProvider(
                credentials.NewStaticCredentialsProvider("test", "test", ""),
            ),
        )
    }

    return config.LoadDefaultConfig(context.TODO(), opts...)
}

Common issues

S3 path style

CloudMock requires path-style S3 access. Always set UsePathStyle: true on the S3 client options. Virtual-hosted style URLs (e.g., bucket.localhost) are not supported.

Module version

The config.WithBaseEndpoint function requires aws-sdk-go-v2 v1.25.0 or later. Earlier versions use per-service endpoint resolvers, which are more verbose to configure.