What is the correct shape of a curl POST request to a gqlgen GraphQL API?

Question

I built a simple GraphQL API extremely similar to gqlgen's "Getting Started" tutorial. I can query it successfully with curl. But I can't get the curl request for mutation right.

schema.graphql:

type Screenshot {
  id: ID!
  url: String!
  filename: String!
  username: String!
  description: String
}

input NewScreenshot {
  id: ID!
  url: String!
  filename: String!
  username: String!
  description: String
}

type Mutation {
  createScreenshot(input: NewScreenshot!): Screenshot!
  deleteScreenshot(id: ID!): String!
}

type Query {
  screenShots(username: String!): [Screenshot!]!
}

models_gen.go:

type NewScreenshot struct {
    ID          string  `json:"id"`
    URL         string  `json:"url"`
    Filename    string  `json:"filename"`
    Username    string  `json:"username"`
    Description *string `json:"description"`
}

type Screenshot struct {
    ID          string  `json:"id"`
    URL         string  `json:"url"`
    Filename    string  `json:"filename"`
    Username    string  `json:"username"`
    Description *string `json:"description"`
}

resolver.go:

func (r *mutationResolver) CreateScreenshot(ctx context.Context, input NewScreenshot) (Screenshot, error) {
    id, err := uuid.NewV4()
    shot := Screenshot{
        ID:          id.String(),
        Description: input.Description,
        URL:         input.URL,
        Filename:    input.Filename,
        Username:    input.Username,
    }

    return shot, nil
}

I've tried:

• Going through the gqlgen documentation, the GraphQL schema, How to GraphQL, and several examples like this and this. And 1.5 days' worth of googling.

• Permutating through a lot, a lot of different shapes in my curl request. This one seems the closest:

  curl -v http://localhost:8080/query
  -H "Content-Type: application/json"
  -d '{ "query":
      { "createScreenshot":
          {"username": "Odour",
           "url": "google.com",
           "description": "just another screenshot",
           "filename": "testimage"
          }
      }
  }'
  

  But it fails with:

  * timeout on name lookup is not supported
  *   Trying ::1...
    % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                               Dload  Upload   Total   Spent    Left  Speed
    0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0* Connected to localhost (::1) port 8080 (#0)
  > POST /query HTTP/1.1
  > Host: localhost:8080
  > User-Agent: curl/7.47.1
  > Accept: */*
  > Content-Type: application/json
  > Content-Length: 146
  >
  } [146 bytes data]
  * upload completely sent off: 146 out of 146 bytes
  < HTTP/1.1 400 Bad Request
  < Date: Sat, 19 Jan 2019 21:00:15 GMT
  < Content-Length: 149
  < Content-Type: text/plain; charset=utf-8
  <
  { [149 bytes data]
  100   295  100   149  100   146    149    146  0:00:01 --:--:--  0:00:01  145k{"errors":[{"message":"json body could not be decoded: json: cannot unmarshal object into Go struct field params.query of type string"}],"data":null}
  * Connection #0 to host localhost left intact
  

Help?

Answer 1

The value of query in the JSON payload needs to be a string containing the GraphQL query, not an object like you are using, for example:

$ curl \
  -H "Content-Type: application/json" \
  -d '{ "query": "mutation { createScreenshot(input: { username: \"Odour\" }) { id } }" }' \
  http://localhost:8080/query

Note that you need to escape the double quotes within the query string.