chore: a better fix for 32-bit unix.Timeval

Why there is no decltype() in Golang?

At least we got generics now.

ref: 9520d84094

app/internal/sockopts/sockopts_linux.go

@@ -7,6 +7,8 @@ import (
 	"net"
 	"time"
 
+	"golang.org/x/exp/constraints"
+
 	"golang.org/x/sys/unix"
 )
 
@@ -58,7 +60,11 @@ func fdControlUnixSocketImpl(c *net.UDPConn, path string) error {
 		}
 		defer unix.Close(socketFd)
 
-		timeout := unixTimeval()
+		var timeout unix.Timeval
+		timeUsec := fdControlUnixTimeout.Microseconds()
+		castAssignInteger(timeUsec/1e6, &timeout.Sec)
+		// Specifying the type explicitly is not necessary here, but it makes GoLand happy.
+		castAssignInteger[int64](timeUsec%1e6, &timeout.Usec)
 
 		_ = unix.SetsockoptTimeval(socketFd, unix.SOL_SOCKET, unix.SO_RCVTIMEO, &timeout)
 		_ = unix.SetsockoptTimeval(socketFd, unix.SOL_SOCKET, unix.SO_SNDTIMEO, &timeout)
@@ -85,3 +91,7 @@ func fdControlUnixSocketImpl(c *net.UDPConn, path string) error {
 		return nil
 	})
 }
+
+func castAssignInteger[F, T constraints.Integer](from F, to *T) {
+	*to = T(from)
+}

app/internal/sockopts/timeval_linux_32.go

@@ -1,15 +0,0 @@
-//go:build linux && (386 || arm || mips || mipsle || ppc)
-
-package sockopts
-
-import (
-	"golang.org/x/sys/unix"
-)
-
-func unixTimeval() unix.Timeval {
-	timeUsec := fdControlUnixTimeout.Microseconds()
-	return unix.Timeval{
-		Sec:  int32(timeUsec / 1e6),
-		Usec: int32(timeUsec % 1e6),
-	}
-}

app/internal/sockopts/timeval_linux_64.go

@@ -1,15 +0,0 @@
-//go:build linux && (amd64 || arm64 || loong64 || mips64 || mips64le || ppc64 || ppc64le || riscv64 || s390x || sparc64)
-
-package sockopts
-
-import (
-	"golang.org/x/sys/unix"
-)
-
-func unixTimeval() unix.Timeval {
-	timeUsec := fdControlUnixTimeout.Microseconds()
-	return unix.Timeval{
-		Sec:  timeUsec / 1e6,
-		Usec: timeUsec % 1e6,
-	}
-}