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serverless-sam-cli-using-debugging-golang.md

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Step-Through Debugging Golang Functions Locally

Golang function step-through debugging is slightly different when compared to Node.js, Java, and Python. We require Delve as the debugger, and wrap your function with it at runtime. The debugger is run in headless mode, listening on the debug port.

When you're debugging, you must compile your function in debug mode:

GOARCH=amd64 GOOS=linux go build -gcflags='-N -l' -o <output path> <path to code directory>

Delve Debugger

You must compile Delve to run in the container and provide its local path with the --debugger-path argument.

Build Delve locally as follows:

GOARCH=amd64 GOOS=linux go build -o <delve folder path>/dlv github.com/go-delve/delve/cmd/dlv

Delve Debugger Path

The output path needs to end in /dlv. The Docker container expects the dlv binary file to be in the <delve folder path>. If it's not, a mounting issue occurs.

Note
The --debugger-path is the path to the directory that contains the dlv binary file that's compiled from the previous code.

Example:

Invoke AWS SAM similar to the following:

sam local start-api -d 5986 --debugger-path <delve folder path>

Delve Debugger API Version

To run the Delve debugger with an API version of your choice, specify the desired API version using an additional debug argument -delveAPI.

Note
For IDEs such as GoLand, Microsoft Visual Studio Code, etc., it is important to run Delve in API version 2 mode.

Example

Invoke AWS SAM with the Delve debugger in API version 2 mode:

sam local start-api -d 5986 --debugger-path <delve folder path> --debug-args "-delveAPI=2"

Example

The following is an example launch configuration for Microsoft Visual Studio Code to attach to a debug session.

{
  "version": "0.2.0",
  "configurations": [
  {
      "name": "Connect to Lambda container",
      "type": "go",
      "request": "launch",
      "mode": "remote",
      "remotePath": "",
      "port": <debug port>,
      "host": "127.0.0.1",
      "program": "${workspaceRoot}",
      "env": {},
      "args": [],
    },
  ]
}