feat: support truncated output and validation error should write in buffer

[zedongh]

for large file validation will cause mess error and output will be huge:

1. support tuncated output should first level validation error
2. validationError GoString concat using byte Buffer for better performance

[santhosh-tekuri]

could you please create individual PR for each commit.

regarding the truncated output, it needs some evaluation from my side and takes time.

since GoString change is simpler and straight forward, having separate PR will help in merge early;

[zedongh]

ok，my pleasure here #111

And, for truncate commit, hope jv support -flag truncate, print few error and stop, rather than print all of error.