Long-Term Debt - Schedule of Long-Term Debt (Details) - USD ($)	Nov. 30, 2019	May 31, 2019
Debt Instrument [Line Items]
Total long-term debt	$ 21,386,471	$ 22,697,464
Debt issuance costs, net of amortization	(38,466)	(37,686)
Total debt, net of debt issuance costs	21,348,005	22,659,778
Less: Current portion of long-term debt	(3,442,269)	(3,030,630)
Long-term debt, net of current portion	17,905,736	19,629,148
Term Loan A Payable to International Bank of Commerce, Prime Rate of Interest Plus 0.5% But Not Less Than 4.0%, Maturing April 30, 2023 [Member]
Debt Instrument [Line Items]
Total long-term debt	2,861,716	3,234,947
Term Loan C Payable to International Bank of Commerce, Prime Rate of Interest Plus 0.5% But Not Less Than 4.0%, Maturing August 4, 2024 [Member]
Debt Instrument [Line Items]
Total long-term debt	1,287,485	1,399,490
Term Loan D Payable to International Bank of Commerce, Prime Rate of Interest Plus 0.5% But Not Less Than 4.75%, Maturing January 10, 2022 [Member]
Debt Instrument [Line Items]
Total long-term debt	1,447,506	1,744,235
Term Loan E Payable to International Bank of Commerce, Prime Rate of Interest Plus 0.5% But Not Less Than 4.75%, Maturing January 10, 2022 [Member]
Debt Instrument [Line Items]
Total long-term debt	814,945	927,199
Term Loan F Payable to International Bank of Commerce, Prime Rate of Interest Plus 0.5% But Not Less Than 5.25%, Maturing February 8, 2021 [Member]
Debt Instrument [Line Items]
Total long-term debt	3,082,407	3,398,247
Term Loan G Payable to International Bank of Commerce, Prime Rate of Interest Plus 0.5% But Not Less Than 5.25%, Maturing April 30, 2024 [Member]
Debt Instrument [Line Items]
Total long-term debt	858,375	876,934
Term Loan H Payable to International Bank of Commerce, Prime Rate of Interest Plus 0.5% But Not Less Than 5.25%, Maturing January 1, 2022 [Member]
Debt Instrument [Line Items]
Total long-term debt	564,067
Revolving Loan Payable to International Bank of Commerce, Prime Rate of Interest Plus 0.5% But Not Less Than 5.5%, Due January 31, 2021 [Member]
Debt Instrument [Line Items]
Total long-term debt	2,923,000	3,205,000
Note Payable to First Bank, Prime Rate of Interest Plus 1.45% But Not Less Than 4.95%, Monthly Principal and Interest Payment of $30,628, Due August 21, 2021, Secured by Production Equipment [Member]
Debt Instrument [Line Items]
Total long-term debt	643,089	800,488
Term Loan Payable by GRE to International Bank of Commerce, Interest Rate of 5.5%, Monthly Principal and Interest Payment of $27,688, Due April 30, 2023 [Member]
Debt Instrument [Line Items]
Total long-term debt	2,362,662	2,461,116
Note Payable to Robert Rosene, 7.5% Interest, Due January 15, 2021 [Member]
Debt Instrument [Line Items]
Total long-term debt	4,340,285	4,426,631
Other [Member]
Debt Instrument [Line Items]
Total long-term debt	$ 200,934	$ 223,177