Unexpected error posting mutation via graphql

Users GraphQL
1

Posting a mutation to standalone:v20.03.1 via /graphql endpoint that works with Altair results in a curious error:

panic: graphql op error:
query:
{"query":"\nmutation AddPerson($person:AddPersonInput!) {\n\taddPerson(input: [$person])\n\t{\n\t  worker {\n\t\temail\n\t\tfirstName\n\t\tlastName\n\t  }\n\t}\n  }  \n","variables":{"person":{"email":"foo@bar.com","firstName":"Foo","lastName":"Bar"}}}
graphql error:
no query string supplied in request

I checked the source for that error, at /graphql/schema/request.go:40

	if req == nil || req.Query == "" {
		return nil, errors.New("no query string supplied in request")
	}

and the test is for the json struct member query which clearly is in the payload. Problem with named operations?

2

Solved. The URL was malformed:

http://localhost:8080//graphql
                      ^

Note the duplicated forward slash after the port.