remove dependency for github.com/dgraph-io/ristretto/z

dgraph-io/ristretto use google/glog. glog rewrites flags on its own, which
causes unexpected behaviour.

helpers.go

@@ -1,18 +1,24 @@
 package nostr
 
 import (
+	"reflect"
 	"sync"
+	"unsafe"
 
-	"github.com/dgraph-io/ristretto/z"
 	"golang.org/x/exp/constraints"
 )
 
 const MAX_LOCKS = 50
 
 var namedMutexPool = make([]sync.Mutex, MAX_LOCKS)
 
+//go:noescape
+//go:linkname memhash runtime.memhash
+func memhash(p unsafe.Pointer, h, s uintptr) uintptr
+
 func namedLock(name string) (unlock func()) {
-	idx := z.MemHashString(name) % MAX_LOCKS
+	ss := (*reflect.StringHeader)(unsafe.Pointer(&name))
+	idx := uint64(memhash(unsafe.Pointer(ss.Data), 0, uintptr(ss.Len))) % MAX_LOCKS
 	namedMutexPool[idx].Lock()
 	return namedMutexPool[idx].Unlock
 }