better Mono wrapper and get groovy with Gradle

futur-api/build.gradle

@@ -0,0 +1,4 @@
+dependencies {
+    implementation("org.jetbrains:annotations:24.1.0")
+    implementation("org.slf4j:slf4j-api:2.0.12")
+}

futur-api/build.gradle.kts

@@ -1,34 +0,0 @@
-import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
-
-plugins {
-    id("java")
-    id("com.github.johnrengelman.shadow") version "7.1.2"
-}
-
-group = "dev.tommyjs"
-version = "2.1.2"
-
-repositories {
-    mavenCentral()
-}
-
-dependencies {
-    implementation("org.jetbrains:annotations:24.1.0")
-    implementation("org.slf4j:slf4j-api:2.0.9")
-    testImplementation(platform("org.junit:junit-bom:5.9.1"))
-    testImplementation("org.junit.jupiter:junit-jupiter")
-}
-
-tasks {
-    build {
-        dependsOn(shadowJar)
-    }
-
-    withType<ShadowJar> {
-        exclude("META-INF/**")
-    }
-}
-
-tasks.test {
-    useJUnitPlatform()
-}

futur-api/src/main/java/dev/tommyjs/futur/promise/AbstractPromise.java

@@ -37,14 +37,13 @@ public abstract class AbstractPromise<T> implements Promise<T> {
 
     @Override
     public T join(long timeoutMillis) throws TimeoutException {
-        PromiseCompletion<T> completion = this.completion.get();
-        if (completion != null) return joinCompletion(completion);
-
+        PromiseCompletion<T> completion;
         long start = System.currentTimeMillis();
         long remainingTimeout = timeoutMillis;
 
         synchronized (this.completion) {
-            while (completion == null && remainingTimeout > 0){
+            completion = this.completion.get();
+            while (completion == null && remainingTimeout > 0) {
                 try {
                     this.completion.wait(remainingTimeout);
                 } catch (InterruptedException e) {