A dependency may only have one s

在flutter项目中添加依赖可能出现如下错误：

Error on line 29, column 5 of pubspec.yaml: A dependency may only have one source.

╷

29 │ ┌ sdk: flutter

30 │ │ english_words: 3.1.0

31 │ │ 

32 │ │ 

33 │ │ # For information on the generic Dart part of this file, see the

34 │ │ # following page: https://www.dartlang.org/tools/pub/pubspec

35 │ │ 

36 │ └ # The following section is specific to Flutter.

╵

pub get failed (65)

这个错误是由于依赖对齐位置没对造成的：

错误示范

改成如下：

正确写法