To get around the limitations described, Facebook developed a new way of doing APIs called GraphQL. It is an API whose style is more compatible with database query constructs, with schemas for different types and a runtime for executing queries and mutations.

GraphQL uses the Schema Definition Language (SDL) to define the schema of various types in the API, as follows:

type Hotel { 
  id: String! 
  displayName: String! 
  city: String ! 
  noRooms: Int 
  starRating: Int 
} 

This is the schema for a hotel. It has four fields: id, displayName, noRooms, and starRating, each with a description of its primitive type. The ! symbol indicates that the field is mandatory.

It is also possible to describe relationships between types. So we can have HotelChain, which has a set of hotels:

type HotelChain { 
  name: String! 
  hotels: [Hotel!]! 
 } 

Here the square bracket indicate an array.

Note that github.com/graphql-go/graphql provides support for graphql in Golang. The following code snippet shows how to define a Golang struct and an equivalent type in graphql:

type Hotel struct { 
   Id          string `json:"id"` 
   DisplayName string `json:"displayName"` 
   City        string `json:"city"` 
   NoRooms     int    `json:"noRooms"` 
   StarRating  int    `json:"starRating"` 
} 

// define custom GraphQL ObjectType `hotelType` for our Golang struct `Hotel` 
// Note that 
// - the fields  map with the json tags for the fields in our struct 
// - the field types match the field type in our struct 
var hotelType = graphql.NewObject(graphql.ObjectConfig{ 
   Name: "Hotel", 
   Fields: graphql.Fields{ 
         "id": &graphql.Field{ 
               Type: graphql.String, 
         }, 
         "displayName": &graphql.Field{ 
               Type: graphql.String, 
         }, 
         "city": &graphql.Field{ 
               Type: graphql.String, 
         }, 
         "noRooms": &graphql.Field{ 
               Type: graphql.Int, 
         }, 
         "starRating": &graphql.Field{ 
               Type: graphql.Int, 
         }, 
   }, 
}) 

Once we have the types, we can then define a schema, with root query and mutation structures:

// define schema, with our rootQuery and rootMutation 
var schema, schemaErr = graphql.NewSchema(graphql.SchemaConfig{ 
   Query:    rootQuery, 
   Mutation: rootMutation, 
}) 

We shall see more details on the rootQuery and rootMutation structures later. This now defines the complete schema needed.