How to Implement Resolvers in gqlgen

Implement resolvers in gqlgen by defining a struct that matches your GraphQL schema types and registering it in resolver.go.

// resolver.go
package resolver

import (
	"github.com/99designs/gqlgen/graphql"
)

type Query struct{}

type Mutation struct{}

type Subscription struct{}

func NewExecutableSchema(cfg Config) graphql.ExecutableSchema {
	return &executableSchema{
		Query:         &Query{},
		Mutation:      &Mutation{},
		Subscription:  &Subscription{},
	}
}

// resolvers.go
package resolver

import (
	"context"
)

func (r *Query) Hello(ctx context.Context) string {
	return "world"
}

// config.go
package resolver

type Config struct{}

Update gqlgen.yml to point to your resolver package:

resolver:
  type: Query
  path: ./resolver.go

Run gqlgen generate to compile the schema and resolvers.

Resolvers are Go functions that fetch data for your GraphQL queries. You define them in a struct that matches your schema, then tell gqlgen where to find them. It's like writing the backend logic that runs when someone asks a question to your API.