Use vendor when building (#201)

* Use vendor code for all go calls

* Add missing vendor dependencies

* Add travis_retry to yarn install

* Fix go test call

vendor/github.com/99designs/gqlgen/plugin/servergen/server.go

@@ -0,0 +1,49 @@
+package servergen
+
+import (
+	"log"
+	"os"
+
+	"github.com/99designs/gqlgen/codegen"
+	"github.com/99designs/gqlgen/codegen/templates"
+	"github.com/99designs/gqlgen/plugin"
+	"github.com/pkg/errors"
+)
+
+func New(filename string) plugin.Plugin {
+	return &Plugin{filename}
+}
+
+type Plugin struct {
+	filename string
+}
+
+var _ plugin.CodeGenerator = &Plugin{}
+
+func (m *Plugin) Name() string {
+	return "servergen"
+}
+func (m *Plugin) GenerateCode(data *codegen.Data) error {
+	serverBuild := &ServerBuild{
+		ExecPackageName:     data.Config.Exec.ImportPath(),
+		ResolverPackageName: data.Config.Resolver.ImportPath(),
+	}
+
+	if _, err := os.Stat(m.filename); os.IsNotExist(errors.Cause(err)) {
+		return templates.Render(templates.Options{
+			PackageName: "main",
+			Filename:    m.filename,
+			Data:        serverBuild,
+		})
+	}
+
+	log.Printf("Skipped server: %s already exists\n", m.filename)
+	return nil
+}
+
+type ServerBuild struct {
+	codegen.Data
+
+	ExecPackageName     string
+	ResolverPackageName string
+}