frequently internal error

[bobooboo]

Issue Type: Bug

In the same environment, the same PC, different time,
internal error frequently occurs.

sometimes, i saw 'The Yang Language Server server crashed 5 times in the last 3 minutes.... ' message.

Extension version: 1.7.0
VS Code version: Code 1.43.0 (78a4c91400152c0f27ba4d363eb56d2835f9903a, 2020-03-09T19:47:57.235Z)
OS version: Windows_NT x64 10.0.18363

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz (12 x 3696)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on oop_rasterization: disabled_off protected_video_decode: enabled rasterization: enabled skia_renderer: disabled_off_ok video_decode: enabled viz_display_compositor: enabled_on viz_hit_test_surface_layer: disabled_off_ok webgl: enabled webgl2: enabled
Load (avg)	undefined
Memory (System)	15.81GB (4.86GB free)
Process Argv
Screen Reader	no
VM	0%