def add_fields(hash)
      timestamp
      fields.deep_merge!(hash, force: true)
      auto_flush

      hash
    end
def add_fields(hash)
      timestamp
      fields.deep_merge!(hash, force: true)
      auto_flush

      hash
    end
Deep-merge fields to the buffer. This will mark the current buffer as
 {pending?} and will result in the eventual flush of the logged data.

 The buffer's timestamp will be initialized with the current time if it
 wasn't set earlier already.

 The buffer will be flushed to all auto_flushing flows automatically. If
 the buffer is not {#buffering?}, it will also be flushed to the non
 auto_flushing flows and cleared afterwards.

 @param hash (see Fields::Hash#deep_merge!)
 @raise (see Fields::Hash#deep_merge!)
 @return [Rackstash::Fields::Hash, ::Hash, Proc] the given `hash` value

 @see Fields::Hash#deep_merge!