Too many watch file handles causing the server to fail to start

[wzshiming]

What version of Hugo are you using (hugo version)?

$ hugo version
v0.88.0

Does this issue reproduce with the latest release?

➜  website git:(master) ✗ hugo server 
Start building sites … 
hugo v0.88.0 darwin/amd64 BuildDate=unknown

                   | FA | NO | EN  
-------------------+----+----+-----
  Pages            | 18 | 76 | 46  
  Paginator pages  |  0 |  0 |  0  
  Non-page files   |  3 |  1 |  3  
  Static files     | 43 | 43 | 43  
  Processed images |  8 |  2 |  8  
  Aliases          |  3 |  0 |  3  
  Sitemaps         |  2 |  1 |  1  
  Cleaned          |  0 |  0 |  0  

Built in 460 ms
Watching for changes in /Users/zsm/website/{assets,content,layouts,package.json,themes}
Watching for config changes in /Users/zsm/website/config.toml, /Users/zsm/website/themes/docsy/config.toml
fatal error: pipe failed

goroutine 1 [running]:
runtime.throw(0x2df23d3, 0xb)
        /Users/zsm/go/go1.16.3/src/runtime/panic.go:1117 +0x72 fp=0xc0056d7878 sp=0xc0056d7848 pc=0x1039592
runtime.sigNoteSetup(0x4087240)
        /Users/zsm/go/go1.16.3/src/runtime/os_darwin.go:98 +0xc5 fp=0xc0056d78a0 sp=0xc0056d7878 pc=0x1035a85
os/signal.signal_enable(0x79fc529500000002)
        /Users/zsm/go/go1.16.3/src/runtime/sigqueue.go:228 +0xa5 fp=0xc0056d78c0 sp=0xc0056d78a0 pc=0x106f925
os/signal.enableSignal(...)
        /Users/zsm/go/go1.16.3/src/os/signal/signal_unix.go:49
os/signal.Notify.func1(0x2)
        /Users/zsm/go/go1.16.3/src/os/signal/signal.go:145 +0x88 fp=0xc0056d78e0 sp=0xc0056d78c0 pc=0x2973ee8
os/signal.Notify(0xc0050afa40, 0xc0056d7b20, 0x2, 0x2)
        /Users/zsm/go/go1.16.3/src/os/signal/signal.go:165 +0x185 fp=0xc0056d7958 sp=0xc0056d78e0 pc=0x2973905
github.com/gohugoio/hugo/commands.(*commandeer).serve(0xc00051b420, 0xc00058de80, 0x0, 0xc0087f5000)
        /Users/zsm/go/src/github.com/gohugoio/hugo/commands/server.go:508 +0x625 fp=0xc0056d7b50 sp=0xc0056d7958 pc=0x29a9aa5
github.com/gohugoio/hugo/commands.(*serverCmd).server(0xc00058de80, 0xc0001c0280, 0x4086850, 0x0, 0x0, 0x0, 0x0)
        /Users/zsm/go/src/github.com/gohugoio/hugo/commands/server.go:286 +0x2e5 fp=0xc0056d7cb0 sp=0xc0056d7b50 pc=0x29a8185
github.com/gohugoio/hugo/commands.(*serverCmd).server-fm(0xc0001c0280, 0x4086850, 0x0, 0x0, 0x0, 0x0)
        /Users/zsm/go/src/github.com/gohugoio/hugo/commands/server.go:133 +0x5b fp=0xc0056d7cf8 sp=0xc0056d7cb0 pc=0x29b6a5b
github.com/spf13/cobra.(*Command).execute(0xc0001c0280, 0x4086850, 0x0, 0x0, 0xc0001c0280, 0x4086850)
        /Users/zsm/go/pkg/mod/github.com/spf13/cobra@v1.2.1/command.go:856 +0x472 fp=0xc0056d7db8 sp=0xc0056d7cf8 pc=0x11d47b2
github.com/spf13/cobra.(*Command).ExecuteC(0xc000808780, 0xc000725720, 0x5, 0x6)
        /Users/zsm/go/pkg/mod/github.com/spf13/cobra@v1.2.1/command.go:974 +0x375 fp=0xc0056d7e98 sp=0xc0056d7db8 pc=0x11d53d5
github.com/gohugoio/hugo/commands.Execute(0xc00003c050, 0x1, 0x1, 0x1007b45, 0xc00010a058, 0x1001570, 0x0)
        /Users/zsm/go/src/github.com/gohugoio/hugo/commands/hugo.go:90 +0xb9 fp=0xc0056d7f28 sp=0xc0056d7e98 pc=0x2994e39
main.main()
        /Users/zsm/go/src/github.com/gohugoio/hugo/main.go:23 +0x76 fp=0xc0056d7f88 sp=0xc0056d7f28 pc=0x29ba416
runtime.main()
        /Users/zsm/go/go1.16.3/src/runtime/proc.go:225 +0x256 fp=0xc0056d7fe0 sp=0xc0056d7f88 pc=0x103bdb6
runtime.goexit()
        /Users/zsm/go/go1.16.3/src/runtime/asm_amd64.s:1371 +0x1 fp=0xc0056d7fe8 sp=0xc0056d7fe0 pc=0x10736e1

goroutine 50 [select]:
go.opencensus.io/stats/view.(*worker).start(0xc0000b0200)
        /Users/zsm/go/pkg/mod/go.opencensus.io@v0.23.0/stats/view/worker.go:276 +0xcd
created by go.opencensus.io/stats/view.init.0
        /Users/zsm/go/pkg/mod/go.opencensus.io@v0.23.0/stats/view/worker.go:34 +0x68

goroutine 348 [syscall]:
syscall.syscall6(0x124e560, 0x7, 0x0, 0x0, 0xc001b8be88, 0xa, 0x4086cb0, 0x0, 0x0, 0x0)
        /Users/zsm/go/go1.16.3/src/runtime/sys_darwin.go:41 +0x2e
golang.org/x/sys/unix.kevent(0x7, 0x0, 0x0, 0xc001b8be88, 0xa, 0x4086cb0, 0x0, 0x0, 0x0)
        /Users/zsm/go/pkg/mod/golang.org/x/sys@v0.0.0-20210630005230-0f9fa26af87c/unix/zsyscall_darwin_amd64.go:276 +0x98
golang.org/x/sys/unix.Kevent(0x7, 0x0, 0x0, 0x0, 0xc001b8be88, 0xa, 0xa, 0x4086cb0, 0x0, 0x0, ...)
        /Users/zsm/go/pkg/mod/golang.org/x/sys@v0.0.0-20210630005230-0f9fa26af87c/unix/syscall_bsd.go:429 +0x71
github.com/fsnotify/fsnotify.read(0x7, 0xc001b8be88, 0xa, 0xa, 0x4086cb0, 0xc001b8be88, 0x0, 0xa, 0x0, 0x0)
        /Users/zsm/go/pkg/mod/github.com/fsnotify/fsnotify@v1.4.9/kqueue.go:511 +0x6e
github.com/fsnotify/fsnotify.(*Watcher).readEvents(0xc008373b60)
        /Users/zsm/go/pkg/mod/github.com/fsnotify/fsnotify@v1.4.9/kqueue.go:274 +0x81b
created by github.com/fsnotify/fsnotify.NewWatcher
        /Users/zsm/go/pkg/mod/github.com/fsnotify/fsnotify@v1.4.9/kqueue.go:62 +0x199

goroutine 349 [select]:
github.com/gohugoio/hugo/watcher.(*Batcher).run(0xc0086556e0)
        /Users/zsm/go/src/github.com/gohugoio/hugo/watcher/batcher.go:67 +0x145
created by github.com/gohugoio/hugo/watcher.New
        /Users/zsm/go/src/github.com/gohugoio/hugo/watcher/batcher.go:56 +0x1c5

goroutine 350 [select]:
github.com/gohugoio/hugo/commands.(*commandeer).newWatcher.func1(0xc0086556e0, 0xc00051b420, 0xc00871b3d8, 0xc0083711a0)
        /Users/zsm/go/src/github.com/gohugoio/hugo/commands/hugo.go:865 +0xdc
created by github.com/gohugoio/hugo/commands.(*commandeer).newWatcher
        /Users/zsm/go/src/github.com/gohugoio/hugo/commands/hugo.go:863 +0x305