Common Patterns That Use Reflection in Go (JSON, ORM, DI)

Go uses reflection primarily in the encoding/json package for marshaling/unmarshaling, in ORMs like GORM for mapping structs to database rows, and in Dependency Injection containers like google/wire for resolving dependencies at runtime.

package main

import (
	"encoding/json"
	"fmt"
)

type User struct {
	Name string `json:"name"`
	Age  int    `json:"age"`
}

func main() {
	u := User{Name: "Alice", Age: 30}
	// encoding/json uses reflection to read struct tags and fields
	data, _ := json.Marshal(u)
	fmt.Println(string(data)) // Output: {"name":"Alice","age":30}
}

Reflection lets your Go program inspect and modify its own structure while it is running, like a program reading its own source code to figure out how to handle data. You use it when you need generic tools, like a JSON converter that works on any data type without you writing specific code for each one. Think of it as a universal adapter that figures out how to plug different shapes into a socket automatically.