v3 refactor (#1868)

* Move to v3

Co-authored-by: Ben Toogood <bentoogood@gmail.com>

server/context.go

@@ -2,22 +2,10 @@ package server
 
 import (
 	"context"
-	"sync"
 )
 
 type serverKey struct{}
 
-func wait(ctx context.Context) *sync.WaitGroup {
-	if ctx == nil {
-		return nil
-	}
-	wg, ok := ctx.Value("wait").(*sync.WaitGroup)
-	if !ok {
-		return nil
-	}
-	return wg
-}
-
 func FromContext(ctx context.Context) (Server, bool) {
 	c, ok := ctx.Value(serverKey{}).(Server)
 	return c, ok