move nostr-sdk repository into here because why not?

sdk/utils.go

@@ -0,0 +1,43 @@
+package sdk
+
+import (
+	"sync"
+	"time"
+)
+
+var (
+	_dtnmtoah     map[string]time.Time
+	_dtnmtoahLock sync.Mutex
+)
+
+func DoThisNotMoreThanOnceAnHour(key string) (doItNow bool) {
+	if _dtnmtoah == nil {
+		go func() {
+			_dtnmtoah = make(map[string]time.Time)
+			for {
+				time.Sleep(time.Minute * 10)
+				_dtnmtoahLock.Lock()
+				now := time.Now()
+				for k, v := range _dtnmtoah {
+					if v.Before(now) {
+						delete(_dtnmtoah, k)
+					}
+				}
+				_dtnmtoahLock.Unlock()
+			}
+		}()
+	}
+
+	_dtnmtoahLock.Lock()
+	defer _dtnmtoahLock.Unlock()
+
+	_, exists := _dtnmtoah[key]
+	return !exists
+}
+
+var serial = 0
+
+func pickNext(list []string) string {
+	serial++
+	return list[serial%len(list)]
+}