suspend funcion throw error about continuation parameter when using kotlin + spring

I was trying to make a RestController using spring+kotlin which is simply as:

    @GetMapping("/test")
    suspend fun test(): Int {
        return 123
    }

And here is my relevant dependencies:

    implementation("org.springframework.boot:spring-boot-starter-webflux")
    implementation("org.springframework:spring-context")
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core")
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-reactive")
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-reactor")

However when I called it, it return with an error

"Invocation failure\nController [com.crypto.tax.admin.controller.AdminController]\nMethod [public final java.lang.Object com.********.test(kotlin.coroutines.Continuation<? super java.lang.Integer>)] with argument values:\n [0] [null] "

Is there any dependency missing or how could I get this up and running?