There are several ways you can share your Canvas course with another instructor:

1. Share your course to Canvas Commons.
https://community.canvaslms.com/t5/Canvas-Commons/How-do-I-share-a-course-to-Commons/ta-p/1793 

The other instructor would then need to import the course from Commons:
https://community.canvaslms.com/t5/Canvas-Commons/How-do-I-import-and-view-a-Commons-resource-in-Canvas/ta-p/1808 

2. Export your course, download the file, and send it to the instructor.
https://community.canvaslms.com/t5/Instructor-Guide/How-do-I-export-a-Canvas-course/ta-p/785 

Then the other instructor would import from that file (Canvas Export Package):
https://community.canvaslms.com/t5/Instructor-Guide/How-do-I-import-a-Canvas-course-export-package/ta-p/795 

3. (Not recommended) Add the other instructor to your course as a teacher or designer through the People menu. Then they would be able to copy from your course.
https://community.canvaslms.com/t5/Instructor-Guide/How-do-I-add-users-to-a-course/ta-p/1119 

Note: If you choose this option, you may need to manually change the course end date in course settings to allow you to add another instructor to the course. Changing the course end date to today's date or later also opens the course back up to students.
https://community.canvaslms.com/t5/Instructor-Guide/How-do-I-change-the-start-and-end-dates-for-a-course/ta-p/452354 

4. Let an Instructional Services Support Staff member know which course to copy (5-digit CRN and semester) and which section it should be copied to. Email [email protected] to submit a request.

If you just want to share an assignment, page, quiz, or module with another instructor (rather than an entire course), you can use Canvas Commons (option 1 above) or use the Send To... option.