code: func (v *Validate) SetMaxStructPoolSize(max int) {
  	structPool = &sync.Pool{New: newStructErrors}
  }
docs: // SetMaxStructPoolSize sets the  struct pools max size. this may be usefull for fine grained
  // performance tuning towards your application, however, the default should be fine for
  // nearly all cases. only increase if you have a deeply nested struct structure.
  // NOTE: this method is not thread-safe
  // NOTE: this is only here to keep compatibility with v5, in v6 the method will be removed