Defined Benefit Pension Plan - Net periodic benefit costs (Details) - USD ($)	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Pension Plan
Interest cost	$ 371,932	$ 398,439
Expected return on plan assets	(671,118)	(672,908)
Amortization of net actuarial loss	215,747	121,990
Net periodic pension income	$ (83,439)	$ (152,479)