Summary - plugin

Combine the plugin structure to write a plugin system.

plugin summary

The flow: build the plugin with -buildmode=plugin → load it with plugin.Open → get the symbol with Lookup → make a safe type assertion to a function or pointer → use it. Errors are checked at every step.

Limits: no Windows, same Go and dependency versions required, no unloading. Because of these, process-based plugin systems are often preferred.

A command registry example

A CLI tool can open every .so file in a plugins/ folder, look up a Komut symbol and register what it finds in a map:

komutlar := map[string]Komut{}
for _, yol := range dosyalar {
    p, err := plugin.Open(yol)
    if err != nil { continue }
    if s, err := p.Lookup("Komut"); err == nil {
        if k, ok := s.(Komut); ok { komutlar[k.Ad()] = k }
    }
}

Exercise Command registry

Define type Komut interface { Ad() string } and type selam struct{}; for selam, Ad() returns "selam". Convert var sym any = selam{} (imitating a plugin symbol) to Komut with a , ok assertion, add it to a map[string]Komut and print the map's length.

Show example solution

package main

import "fmt"

type Komut interface{ Ad() string }

type selam struct{}

func (selam) Ad() string { return "selam" }

func main() {
    komutlar := map[string]Komut{}
    var sym any = selam{}
    if k, ok := sym.(Komut); ok {
        komutlar[k.Ad()] = k
    }
    fmt.Println(len(komutlar))
}

Test yourself

Which is a common alternative to plugins?
- sync.Pool
- Talking to a separate process over gRPC/RPC
- unsafe.Pointer
- go:embed
Show answer

Talking to a separate process over gRPC/RPC — Systems such as HashiCorp go-plugin run the plugin in a separate process, removing version coupling and platform limits.

Build mode

go build -buildmode=____ -o ek.so ./ek

Show answer

go build -buildmode=plugin -o ek.so ./ek

Flow

-buildmode=plugin

Build
plugin.Open

Load
Lookup

Symbol
s.(Komut)

Type assertion

Next lesson: The database/sql package

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