This is rather mysterious but the first thing I did after installing the Windows binary (ripgrep-0.1.17-x86_64-pc-windows-msvc.zip) was to run rg fun from Cygwin shell inside a relatively big repository and it just hung without outputting anything. Trying to search inside a single file works fine, searching in a single leaf subdirectory does too, but searching under a subdirectory containing other subdirectories outputs a number of matches and then hangs on exit. To emphasize, this only happens in a Cygwin shell, the tool doesn't hang when run from the standard Windows DOS window.

Looking at it in process explorer I see that the thread is completely stuck (0% CPU use) and the stack is

ntoskrnl.exe!KiSwapContext+0x7a
ntoskrnl.exe!KiCommitThreadWait+0x1d2
ntoskrnl.exe!KeWaitForSingleObject+0x19f
ntoskrnl.exe!KiSuspendThread+0x54
ntoskrnl.exe!KiDeliverApc+0x21d
ntoskrnl.exe!KiCommitThreadWait+0x3dd
ntoskrnl.exe!KeWaitForSingleObject+0x19f
ntoskrnl.exe!NtReadFile+0x8ae
ntoskrnl.exe!KiSystemServiceCopyEnd+0x13
ntdll.dll!NtReadFile+0xa
KERNELBASE.dll!ReadFile+0x76
kernel32.dll!ReadFileImplementation+0x55
rg.exe+0x124f1f

which doesn't make much sense to me, but maybe it can be useful to you if you have the map file and see what does 0x124f1f offset correspond to.

I could try debugging this further later, but unfortunately I really don't have time for this now, I just wanted to quickly check a promising new tool...