diff --git a/chronos/asyncproc.nim b/chronos/asyncproc.nim
index 8615c57..f008776 100644
--- a/chronos/asyncproc.nim
+++ b/chronos/asyncproc.nim
@@ -231,8 +231,9 @@ proc closeProcessHandles(pipes: var AsyncProcessPipes,
                          lastError: OSErrorCode): OSErrorCode {.apforward.}
 proc closeProcessStreams(pipes: AsyncProcessPipes,
                          options: set[AsyncProcessOption]): Future[void] {.
-     apforward.}
-proc closeWait(holder: AsyncStreamHolder): Future[void] {.apforward.}
+     async: (raises: []).}
+proc closeWait(holder: AsyncStreamHolder): Future[void] {.
+     async: (raises: []).}
 
 template isOk(code: OSErrorCode): bool =
   when defined(windows):
@@ -391,7 +392,8 @@ when defined(windows):
                      stdinHandle = ProcessStreamHandle(),
                      stdoutHandle = ProcessStreamHandle(),
                      stderrHandle = ProcessStreamHandle(),
-                    ): Future[AsyncProcessRef] {.async.} =
+                    ): Future[AsyncProcessRef] {.
+       async: (raises: [AsyncProcessError, CancelledError]).} =
     var
       pipes = preparePipes(options, stdinHandle, stdoutHandle,
                            stderrHandle).valueOr:
@@ -517,14 +519,16 @@ when defined(windows):
       ok(false)
 
   proc waitForExit*(p: AsyncProcessRef,
-                    timeout = InfiniteDuration): Future[int] {.async.} =
+                    timeout = InfiniteDuration): Future[int] {.
+       async: (raises: [AsyncProcessError, AsyncProcessTimeoutError,
+                 CancelledError]).} =
     if p.exitStatus.isSome():
       return p.exitStatus.get()
 
     let wres =
       try:
         await waitForSingleObject(p.processHandle, timeout)
-      except ValueError as exc:
+      except AsyncError as exc:
         raiseAsyncProcessError("Unable to wait for process handle", exc)
 
     if wres == WaitableResult.Timeout:
@@ -537,7 +541,8 @@ when defined(windows):
 
     if exitCode >= 0:
       p.exitStatus = Opt.some(exitCode)
-    return exitCode
+
+    exitCode
 
   proc peekExitCode(p: AsyncProcessRef): AsyncProcessResult[int] =
     if p.exitStatus.isSome():
@@ -787,7 +792,8 @@ else:
                      stdinHandle = ProcessStreamHandle(),
                      stdoutHandle = ProcessStreamHandle(),
                      stderrHandle = ProcessStreamHandle(),
-                    ): Future[AsyncProcessRef] {.async.} =
+                    ): Future[AsyncProcessRef] {.
+       async: (raises: [AsyncProcessError, CancelledError]).} =
     var
       pid: Pid
       pipes = preparePipes(options, stdinHandle, stdoutHandle,
@@ -887,7 +893,7 @@ else:
     )
 
     trackCounter(AsyncProcessTrackerName)
-    return process
+    process
 
   proc peekProcessExitCode(p: AsyncProcessRef,
                            reap = false): AsyncProcessResult[int] =
@@ -948,7 +954,9 @@ else:
       ok(false)
 
   proc waitForExit*(p: AsyncProcessRef,
-                    timeout = InfiniteDuration): Future[int] =
+                    timeout = InfiniteDuration): Future[int] {.
+       async: (raw: true, raises: [
+               AsyncProcessError, AsyncProcessTimeoutError, CancelledError]).} =
     var
       retFuture = newFuture[int]("chronos.waitForExit()")
       processHandle: ProcessHandle
@@ -1050,7 +1058,7 @@ else:
 
     # Process is still running, so we going to wait for SIGCHLD.
     retFuture.cancelCallback = cancellation
-    return retFuture
+    retFuture
 
   proc peekExitCode(p: AsyncProcessRef): AsyncProcessResult[int] =
     let res = ? p.peekProcessExitCode()
@@ -1155,7 +1163,7 @@ proc preparePipes(options: set[AsyncProcessOption],
     stderrHandle: remoteStderr
   ))
 
-proc closeWait(holder: AsyncStreamHolder) {.async.} =
+proc closeWait(holder: AsyncStreamHolder) {.async: (raises: []).} =
   let (future, transp) =
     case holder.kind
     of StreamKind.None:
@@ -1182,10 +1190,11 @@ proc closeWait(holder: AsyncStreamHolder) {.async.} =
       res
 
   if len(pending) > 0:
-    await allFutures(pending)
+    await noCancel allFutures(pending)
 
 proc closeProcessStreams(pipes: AsyncProcessPipes,
-                         options: set[AsyncProcessOption]): Future[void] =
+                         options: set[AsyncProcessOption]): Future[void] {.
+     async: (raw: true, raises: []).} =
   let pending =
     block:
       var res: seq[Future[void]]
@@ -1196,10 +1205,12 @@ proc closeProcessStreams(pipes: AsyncProcessPipes,
       if ProcessFlag.AutoStderr in pipes.flags:
         res.add(pipes.stderrHolder.closeWait())
       res
-  allFutures(pending)
+  noCancel allFutures(pending)
 
 proc opAndWaitForExit(p: AsyncProcessRef, op: WaitOperation,
-                      timeout = InfiniteDuration): Future[int] {.async.} =
+                      timeout = InfiniteDuration): Future[int] {.
+     async: (raises: [
+      AsyncProcessError, AsyncProcessTimeoutError, CancelledError]).} =
   let timerFut =
     if timeout == InfiniteDuration:
       newFuture[void]("chronos.killAndwaitForExit")
@@ -1223,7 +1234,10 @@ proc opAndWaitForExit(p: AsyncProcessRef, op: WaitOperation,
       return exitCode
 
     let waitFut = p.waitForExit().wait(100.milliseconds)
-    discard await race(FutureBase(waitFut), FutureBase(timerFut))
+    try:
+      discard await race(FutureBase(waitFut), FutureBase(timerFut))
+    except ValueError:
+      raiseAssert "This should not be happened!"
 
     if waitFut.finished() and not(waitFut.failed()):
       let res = p.peekExitCode()
@@ -1237,25 +1251,28 @@ proc opAndWaitForExit(p: AsyncProcessRef, op: WaitOperation,
         await waitFut.cancelAndWait()
       raiseAsyncProcessTimeoutError()
 
-proc closeWait*(p: AsyncProcessRef) {.async.} =
+proc closeWait*(p: AsyncProcessRef) {.async: (raises: []).} =
   # Here we ignore all possible errrors, because we do not want to raise
   # exceptions.
   discard closeProcessHandles(p.pipes, p.options, OSErrorCode(0))
-  await noCancel(p.pipes.closeProcessStreams(p.options))
+  await p.pipes.closeProcessStreams(p.options)
   discard p.closeThreadAndProcessHandle()
   untrackCounter(AsyncProcessTrackerName)
 
 proc stdinStream*(p: AsyncProcessRef): AsyncStreamWriter =
+  ## Returns STDIN async stream associated with process `p`.
   doAssert(p.pipes.stdinHolder.kind == StreamKind.Writer,
            "StdinStreamWriter is not available")
   p.pipes.stdinHolder.writer
 
 proc stdoutStream*(p: AsyncProcessRef): AsyncStreamReader =
+  ## Returns STDOUT async stream associated with process `p`.
   doAssert(p.pipes.stdoutHolder.kind == StreamKind.Reader,
            "StdoutStreamReader is not available")
   p.pipes.stdoutHolder.reader
 
 proc stderrStream*(p: AsyncProcessRef): AsyncStreamReader =
+  ## Returns STDERR async stream associated with process `p`.
   doAssert(p.pipes.stderrHolder.kind == StreamKind.Reader,
            "StderrStreamReader is not available")
   p.pipes.stderrHolder.reader
@@ -1263,7 +1280,9 @@ proc stderrStream*(p: AsyncProcessRef): AsyncStreamReader =
 proc execCommand*(command: string,
                   options = {AsyncProcessOption.EvalCommand},
                   timeout = InfiniteDuration
-                 ): Future[int] {.async.} =
+                 ): Future[int] {.
+     async: (raises: [
+      AsyncProcessError, AsyncProcessTimeoutError, CancelledError]).} =
   let
     poptions = options + {AsyncProcessOption.EvalCommand}
     process = await startProcess(command, options = poptions)
@@ -1277,7 +1296,9 @@ proc execCommand*(command: string,
 proc execCommandEx*(command: string,
                     options = {AsyncProcessOption.EvalCommand},
                     timeout = InfiniteDuration
-                   ): Future[CommandExResponse] {.async.} =
+                   ): Future[CommandExResponse] {.
+     async: (raises: [
+      AsyncProcessError, AsyncProcessTimeoutError, CancelledError]).} =
   let
     process = await startProcess(command, options = options,
                                  stdoutHandle = AsyncProcess.Pipe,
@@ -1291,13 +1312,13 @@ proc execCommandEx*(command: string,
           status = await process.waitForExit(timeout)
           output =
             try:
-              string.fromBytes(outputReader.read())
+              string.fromBytes(await outputReader)
             except AsyncStreamError as exc:
               raiseAsyncProcessError("Unable to read process' stdout channel",
                                      exc)
           error =
             try:
-              string.fromBytes(errorReader.read())
+              string.fromBytes(await errorReader)
             except AsyncStreamError as exc:
               raiseAsyncProcessError("Unable to read process' stderr channel",
                                      exc)
@@ -1308,13 +1329,15 @@ proc execCommandEx*(command: string,
   res
 
 proc pid*(p: AsyncProcessRef): int =
-  ## Returns process ``p`` identifier.
+  ## Returns process ``p`` unique process identifier.
   int(p.processId)
 
 template processId*(p: AsyncProcessRef): int = pid(p)
 
 proc killAndWaitForExit*(p: AsyncProcessRef,
-                         timeout = InfiniteDuration): Future[int] =
+                         timeout = InfiniteDuration): Future[int] {.
+     async: (raw: true, raises: [
+      AsyncProcessError, AsyncProcessTimeoutError, CancelledError]).} =
   ## Perform continuous attempts to kill the ``p`` process for specified period
   ## of time ``timeout``.
   ##
@@ -1330,7 +1353,9 @@ proc killAndWaitForExit*(p: AsyncProcessRef,
   opAndWaitForExit(p, WaitOperation.Kill, timeout)
 
 proc terminateAndWaitForExit*(p: AsyncProcessRef,
-                              timeout = InfiniteDuration): Future[int] =
+                              timeout = InfiniteDuration): Future[int] {.
+     async: (raw: true, raises: [
+       AsyncProcessError, AsyncProcessTimeoutError, CancelledError]).} =
   ## Perform continuous attempts to terminate the ``p`` process for specified
   ## period of time ``timeout``.
   ##