how to change 'return' button in keyboard?

Update 2019: Using version react-native 0.57 the accepted answer is no longer valid as "Go" is not one of the accepted values, use "go" without capitalisation instead

Actual react-native 0.57 contract states the following enums:

    /**
     * enum('default', 'go', 'google', 'join', 'next', 'route', 'search', 'send', 'yahoo', 'done', 'emergency-call')
     * Determines how the return key should look.
     */
    returnKeyType?: ReturnKeyTypeOptions;

Update for 2019 - RN 0.57 changed the key from "Go" to "go"

you should use returnKeyType property to determine how the return key should look

Example:

 <TextInput style={{height:40}} 
       placeholder="Input"
       placeholderTextColor="#DCDCDC"
       returnKeyType="go"
 />