POTUS could call a special session of Congress to finish the FY2019 appropriations

As in many years, Congress has relied on continuing resolutions instead of performing their Constitutional duty to pass appropriations in a timely manner for the fiscal year. Several appropriations are outstanding in committees since late June and the current continuation resolution funds the federal agencies thru December 21, 2018. The current session of Congress has not fulfilled their duty and should not be permitted to adjourn until that duty is fulfilled. If the impasse continues, the President should invoke his Constitutional authority under Article II Section 3 to call a special session of Congress.

“… he may, on extraordinary occasions, convene both Houses, or either of them, and in case of disagreement between them, with respect to the time of adjournment, he may adjourn them to such time as he shall think proper.”

Status of Appropriations at congress.gov

https://www.congress.gov/resources/display/content/Appropriations+for+Fiscal+Year+2019

US Constitution

Article II

Section 3.

He shall from time to time give to the Congress information of the state of the union, and recommend to their consideration such measures as he shall judge necessary and expedient; he may, on extraordinary occasions, convene both Houses, or either of them, and in case of disagreement between them, with respect to the time of adjournment, he may adjourn them to such time as he shall think proper; he shall receive ambassadors and other public ministers; he shall take care that the laws be faithfully executed, and shall commission all the officers of the United States.

https://www.law.cornell.edu/constitution/articleii