fixed initialism errors in accordance with golang conventions in 7 files. (#24287)

server/channels/utils/file.go

@@ -8,7 +8,7 @@ import (
 	"io"
 )
 
-var SizeLimitExceeded = errors.New("Size limit exceeded")
+var ErrSizeLimitExceeded = errors.New("size limit exceeded")
 
 type LimitedReaderWithError struct {
 	limitedReader *io.LimitedReader
@@ -23,7 +23,7 @@ func NewLimitedReaderWithError(reader io.Reader, maxBytes int64) *LimitedReaderW
 func (l *LimitedReaderWithError) Read(p []byte) (int, error) {
 	n, err := l.limitedReader.Read(p)
 	if l.limitedReader.N <= 0 && err == io.EOF {
-		return n, SizeLimitExceeded
+		return n, ErrSizeLimitExceeded
 	}
 	return n, err
 }