How Can I Dynamically Link External Go Code to an Existing Go Binary?

Building and Linking Dynamically from a Go Binary

Consider a situation where you have an existing Go binary and need to incorporate external code into it dynamically. This can be achieved by compiling the external Go file and linking it to the existing binary.

Compiling External Go File

Once Go 1.5 is released in August 2015, support for shared libraries will be introduced. Using the -buildmode=shared flag, you can build the external Go file as a shared library:

go install -buildmode=shared external.go

Linking Compiled Code

To link the compiled shared library to the existing binary, use the -linkshared flag during the build process:

go build -linkshared main.go

Example Usage

In the given example, the main binary would contain the following code:

func main() {
    // Compile external package containing runFoo()
    pkg, err := build.Import("github.com/example/external", "", build.ImportModeShared)
    if err != nil {
        // Handle error
    }

    // Get runFoo function from compiled package
    runFoo := reflect.ValueOf(pkg.Func("runFoo"))

    // Call the compiled runFoo function
    runFoo.Call(nil)

    // Continue execution normally
}

This approach allows you to dynamically incorporate new functionality into existing Go binaries without rebuilding the entire program.

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