Add Coroutines sample

samples/build.gradle

@@ -1,4 +1,7 @@
-apply plugin: 'java-library'
+plugins {
+  id 'java-library'
+  alias libs.plugins.kotlin.jvm
+}
 
 dependencies {
   implementation projects.retrofit
@@ -10,5 +13,6 @@ dependencies {
   implementation libs.mockwebserver
   implementation libs.guava
   implementation libs.jsoup
+  implementation libs.kotlinCoroutines
   compileOnly libs.findBugsAnnotations
 }

samples/src/main/java/com/example/retrofit/KotlinCoroutines.kt

@@ -0,0 +1,53 @@
+package com.example.retrofit
+
+import retrofit2.ResultCallAdapterFactory
+import retrofit2.Retrofit
+import retrofit2.converter.gson.GsonConverterFactory
+import retrofit2.create
+import retrofit2.http.GET
+import retrofit2.http.Path
+
+data class Contributor(val login: String, val contributions: Int)
+
+interface GitHub {
+  @GET("/repos/{owner}/{repo}/contributors")
+  suspend fun getContributors(
+    @Path("owner") owner: String,
+    @Path("repo") repo: String,
+  ): List<Contributor>
+
+  @GET("/repos/{owner}/{repo}/contributors")
+  suspend fun getContributorsWithResult(
+    @Path("owner") owner: String,
+    @Path("repo") repo: String,
+  ): Result<List<Contributor>>
+}
+
+suspend fun main() {
+  val retrofit = Retrofit.Builder()
+    .baseUrl("https://api.github.com")
+    .addCallAdapterFactory(ResultCallAdapterFactory.create())
+    .addConverterFactory(GsonConverterFactory.create())
+    .build()
+  val github: GitHub = retrofit.create()
+
+  println("Request without Result using")
+  try {
+    github.getContributors("square", "retrofit").forEach { contributor ->
+      println(contributor)
+    }
+  } catch (e: Exception) {
+    println("An error occurred when not using Result: $e")
+  }
+
+  println("Request with Result using")
+  github.getContributorsWithResult("square", "retrofit")
+    .onSuccess {
+      it.forEach { contributor ->
+        println(contributor)
+      }
+    }
+    .onFailure {
+      println("An error occurred when using Result: $it")
+    }
+}