add simple gql federation server

.gitignore

@@ -4,4 +4,4 @@
 .DS_Store
 pkg/parser/testdata/lotto.graphql
 *node_modules*
-/vendor
+*vendor*

examples/federation/accounts/gqlgen.yml

@@ -0,0 +1,55 @@
+# Where are all the schema files located? globs are supported eg  src/**/*.graphqls
+schema:
+  - graph/*.graphqls
+
+# Where should the generated server code go?
+exec:
+  filename: graph/generated/generated.go
+  package: generated
+
+federation:
+  filename: graph/generated/federation.go
+  package: generated
+
+# Where should any generated models go?
+model:
+  filename: graph/model/models_gen.go
+  package: model
+
+# Where should the resolver implementations go?
+resolver:
+  layout: follow-schema
+  dir: graph
+  package: graph
+
+# Optional: turn on use `gqlgen:"fieldName"` tags in your models
+# struct_tag: json
+
+# Optional: turn on to use []Thing instead of []*Thing
+# omit_slice_element_pointers: false
+
+# Optional: set to speed up generation time by not performing a final validation pass.
+# skip_validation: true
+
+# gqlgen will search for any type names in the schema in these go packages
+# if they match it will use them, otherwise it will generate them.
+autobind:
+  - "github.com/99designs/gqlgen/example/federation/accounts/graph/model"
+
+# This section declares type mapping between the GraphQL and go type systems
+#
+# The first line in each type will be used as defaults for resolver arguments and
+# modelgen, the others will be allowed when binding to fields. Configure them to
+# your liking
+models:
+  ID:
+    model:
+      - github.com/99designs/gqlgen/graphql.ID
+      - github.com/99designs/gqlgen/graphql.Int
+      - github.com/99designs/gqlgen/graphql.Int64
+      - github.com/99designs/gqlgen/graphql.Int32
+  Int:
+    model:
+      - github.com/99designs/gqlgen/graphql.Int
+      - github.com/99designs/gqlgen/graphql.Int64
+      - github.com/99designs/gqlgen/graphql.Int32

examples/federation/accounts/graph/entity.resolvers.go

@@ -0,0 +1,28 @@
+package graph
+
+// This file will be automatically regenerated based on the schema, any resolver implementations
+// will be copied through when generating and any unknown code will be moved to the end.
+
+import (
+	"context"
+	generated1 "federation/accounts/graph/generated"
+
+	"github.com/99designs/gqlgen/example/federation/accounts/graph/model"
+)
+
+func (r *entityResolver) FindUserByID(ctx context.Context, id string) (*model.User, error) {
+	name := "User " + id
+	if id == "1234" {
+		name = "Me"
+	}
+
+	return &model.User{
+		ID:       id,
+		Username: name,
+	}, nil
+}
+
+// Entity returns generated1.EntityResolver implementation.
+func (r *Resolver) Entity() generated1.EntityResolver { return &entityResolver{r} }
+
+type entityResolver struct{ *Resolver }