Add explicit coroutine context to CoWebExceptionHandler

spring-web/src/main/kotlin/org/springframework/web/server/CoWebExceptionHandler.kt

@@ -3,11 +3,13 @@ package org.springframework.web.server
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.reactor.mono
 import reactor.core.publisher.Mono
+import kotlin.coroutines.CoroutineContext
 
 abstract class CoWebExceptionHandler : WebExceptionHandler {
-	final override fun handle(exchange: ServerWebExchange, ex: Throwable): Mono<Void> =
-		mono(Dispatchers.Unconfined) { coHandle(exchange, ex) }.then()
-
+	final override fun handle(exchange: ServerWebExchange, ex: Throwable): Mono<Void> {
+		val context = exchange.attributes[CoWebFilter.COROUTINE_CONTEXT_ATTRIBUTE] as CoroutineContext?
+		return mono(context ?: Dispatchers.Unconfined) { coHandle(exchange, ex) }.then()
+	}
 
 	protected abstract suspend fun coHandle(exchange: ServerWebExchange, ex: Throwable)
 }