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AWS Lambda with Go - How to Build, Deploy, and Invoke

#aws #go #lambda

Build, Deploy, and Invoke AWS Lambda Functions in Golang

1. Initialize Lambda main function & handler in Go

  • Go Lambda starts from the main() function, usually with lambda.Start(handler).
  • Handler function signatures: 
  func ()
  func () error
  func () (TOut, error)
  func (TIn) error
  func (TIn) (TOut, error)
  func (context.Context) error
  func (context.Context) (TOut, error)
  func (context.Context, TIn) error
  func (context.Context, TIn) (TOut, error)
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  • ctx: context for timeout, logs, request ID
  • TIn and TOut represent types that can be Unmarshal JSON.

Example:

```go
package main

import (
    "context"
    "github.com/aws/aws-lambda-go/lambda"
)

type MyEvent struct {
    Name string `json:"name"`
}

func handler(ctx context.Context, e MyEvent) (string, error) {
    return "Hello " + e.Name, nil
}

func main() {
    lambda.Start(handler)
}
```
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2. Deployment methods

(a) Zip deployment

GOOS=linux GOARCH=amd64 go build -o bootstrap main.go
zip function.zip bootstrap
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Upload function.zip to Lambda.

(b) Docker container deployment
Dockerfile example:

FROM public.ecr.aws/lambda/go:1
COPY main ${LAMBDA_TASK_ROOT}
CMD ["main"]
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Push the image to ECR and deploy.

3. Invocation methods

AWS CLI

aws lambda invoke --function-name MyFunction --payload '{"name":"Jack"}' response.json
cat response.json
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Go SDK (aws-sdk-go-v2)

client := lambda.NewFromConfig(cfg)
resp, err := client.Invoke(context.TODO(), &lambda.InvokeInput{
    FunctionName: aws.String("MyFunction"),
    Payload:      []byte(`{"name":"Jack"}`),
})
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4. Create & Update Lambda Function via AWS CLI

Create function (ZIP deployment)

aws lambda create-function \
  --function-name MyFunction \
  --runtime go1.x \
  --role arn:aws:iam::<account-id>:role/<lambda-execution-role> \
  --handler bootstrap \
  --zip-file fileb://function.zip
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Update function code (ZIP deployment)

aws lambda update-function-code \
  --function-name MyFunction \
  --zip-file fileb://function.zip
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References

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