listClusters 
  inline suspend fun EcsClient.listClusters(crossinline block: ListClustersRequest.Builder.() -> Unit): ListClustersResponse
Returns a list of existing clusters.
Samples
fun main() { 
   //sampleStart 
   // This example lists all of your available clusters in your default region.
val resp = ecsClient.listClusters() 
   //sampleEnd
}