exporters/trace/jaeger test compilation error

[MrAlias]

Testing on Windows (Go 1.15 arch=amd64):

# go.opentelemetry.io/otel/exporters/trace/jaeger [go.opentelemetry.io/otel/exporters/trace/jaeger.test]
Error: .\reconnecting_udp_client_test.go:87:45: cannot use int(fd.Fd()) (type int) as type syscall.Handle in argument to syscall.GetsockoptInt
FAIL	go.opentelemetry.io/otel/exporters/trace/jaeger [build failed]

I am able to reproduce this locally on a linux system:

$ cd exporters/trace/jaeger
$ GOOS=windows go test .
# go.opentelemetry.io/otel/exporters/trace/jaeger [go.opentelemetry.io/otel/exporters/trace/jaeger.test]
./reconnecting_udp_client_test.go:87:45: cannot use int(fd.Fd()) (type int) as type syscall.Handle in argument to syscall.GetsockoptInt
FAIL	go.opentelemetry.io/otel/exporters/trace/jaeger [build failed]
FAIL

It looks like we use the low level syscall package with a unix specific calling signature:

opentelemetry-go/exporters/trace/jaeger/reconnecting_udp_client_test.go

Line 87 in 4a163be

bufferBytes, _ := syscall.GetsockoptInt(int(fd.Fd()), syscall.SOL_SOCKET, syscall.SO_SNDBUF)

The unix function signature for syscall.GetsockoptInt:

func GetsockoptInt(fd, level, opt int) (value int, err error)

Where the windows signature is:

func GetsockoptInt(fd Handle, level, opt int) (int, error)