Add security handler (#8)

security/handler.go

@@ -0,0 +1,18 @@
+package security
+
+import (
+	"net/http"
+)
+
+func Handler(handler http.HandlerFunc, security *Config) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		usernameEntered, passwordEntered, ok := r.BasicAuth()
+		if !ok || usernameEntered != security.Basic.Username || Sha512(passwordEntered) != security.Basic.PasswordSha512Hash {
+			w.Header().Set("WWW-Authenticate", "Basic")
+			w.WriteHeader(http.StatusUnauthorized)
+			_, _ = w.Write([]byte("Unauthorized"))
+			return
+		}
+		handler(w, r)
+	}
+}